There's a totally underestimated challenge to playing DCS A-10. I have a looong way to go, but I want to share some of the things that have made me feel more confident, and also some of the things I just think are plain cool about it.
DCS is a "game" on several levels. First of all, obviously, you are given tasks to complete. You can bumble your way through some of these and come out with a mission complete. My first few campaign missions were like that. Just remembering how to fire a maverick and using mavericks until i had none, then throwing some mk82s around and pretend like i knew what i was doing, all the while largely ignoring the JTAC or radio chatter, because damn if I could understand a word of what those dudes were saying anyway. In this way, you can kind of subjectively enjoy the experience, but you will feel like an idiot all the while you're doing it.
This is kind of "it" with a sim like this, I feel: The REAL challenge is self-imposed; Can I do this kind of stuff correctly? Can I be legitimately good? Merely getting by will never be satisfying, but with no real "scoring system" beyond a binary success/failure, the quality of your skill is largely something you either judge yourself, by the goals you set for yourself and how efficiently you attain them by your own standards.
This is cool, because paired with a simple understanding of the mission editor you are allowed to ramp up the difficuly and thus the learning curve according to your own standards. This is a game that, right out of the gate, has no problems thoroughly humbling you, and as a result you get this kind of fear of failing. I spent weeks just starting up, taking off and just flying around, never mind learning any of the avionics properly beyond that. Just getting off the ground felt like a feat.
(note. I'm typing this on my laptop; When I get back to my gaming box I'll edit in some screenshots for illustration.)
The mission editor
The mission editor can look incredibly dense if you boot it up, but all you really need to know to make some scenarios for yourself and your own practise routines is how to create an A-10, outfit it, put yourself in it and create some other units to interact with. So, step by step:
1. To scroll around the map, right click and drag. To zoom in and out, use the mouse wheel. Around the map are a bunch of airfields, most marked with a long arrow along their runway and a geomagnetic heading, as well as a name. Pick one you want to start from.
2. On the far left is a vertical row of icons representing various unit classes. Pick the one that looks like a fighter jet. Then click on the airfield you picked on the map. An icon marked 'A' will appear.
3. The default plane at any point is the last one you had selected from the plane group. The default at the start is an USA A-10C, which is what we want. On the top right is the property inspector for the currently selected mission object, which will list the group the plane is assigned to, the plane type and more. From the "skill" dropdown, you want to pick "player".
4. At this point, you've already got a mission that will put you in an unarmed A-10C mid flight over the airfield of your choice. This might be all you need to have some simple flight. To fly, click on the blue check mark button on the middle left.
5. To change the initial state of your plane, for instance setting it up for takeoff from the runway, you need to select the plane icon again, and look at the very bottom of the right column. This contains 4 tabs, and the ones we care about are the first two; the first is the "waypoint" tab, and the second is the "ordnance" tab. With the plane selected, the waypoint tab will be containing info on the initial position of the plane. From the "type" dropdown, given that the plane is near an airfield, you can pick "takeoff from ramp" if you want to cold start the jet, or "takeoff from runway" if you want to be ready for takeoff immediately. In either case, the editor will move the plane to a position that makes sense.
6. Clicking the ordnance tab will bring up a full screen view with a vertical list of various loadouts you can pick and customise. This is a pretty intuitive screen; Just pick one from the list, or right click a hardpoint to change its load.
7. Bam, you have a plane with guns on it. For some simple practise, take off and shoot up your own airfield ;-)
8. If you want "real" stuff to shoot at, mess with the other object categories and create some tanks or trucks. Of course scripting a proper mission is much more involved, but this should get you started. Also, don't forget the "encyclopedia" you can bring up from the top menu bar. Very handy.
On being inside and being outside
There's a lot going on inside that cockpit, and while you're juggling your targeting pod, map and ordnance, it can be easy to lose track of what's going on on the outside. Most MFD pages have an attitude indicator in the lower left of the display to help you make sure you're not pointing at mother earth while you've got your head down trying to move your TGP onto some tank to your west, but that doesn't necessarily aid your sensory awareness to any large extent.
One term I picked up from the book Warthog was the dichotomy between being "inside", where your attention is focused on the interior of the cockpit, and being "outside", where you are actively looking out of the canopy while maneuvering. Let me tell you, no manner of careful use of the moving map display is going to make you as aware of where you are at in relation to your target as simply looking out the window.
While these two will blend together sometimes, I feel it's helped me a lot to consciously move between the two. For instance, I'll be "inside" when I'm observing the area, looking for targets, setting up mission markpoints for targets I want to hit etc. This typically takes place at "angels 15" (which is a fancy way of saying 15000ft) or higher, where I'm relatively safe from most AAA, and I can set the plane in an autopilot-assisted orbit, letting me focus on the office work of observing and preparing. Then, when I'm going in, I've already done all the time consuming work, and I can do most of my attack work through the HUD, assisted with glancing at the TGP. Ideally, once you're "outside", you shouldn't have to be doing any complex strategic decisions, only split second tactical ones.
A key here is that no matter how well versed you are with the HOTAS controls, when "inside" you will still need to click on buttons with your mouse. You do NOT want to be doing this while things are firing at you. Knowing when to be "inside" and when to be "outside" is probably the single best advice I can give. When you've been circling a town for 20 minutes, it helps to have a good visual idea of its layout beyond the map.
From markpoint to waypoint
The first thing you will be doing when attacking an area is to make sure there is no active mid to long range AAA. The worst thing you want to conceivably have to deal with is machine gun fire, and you'd rather not deal with that either. This is why the A-10 carries long range mavericks, so you can get rid of all that crap before you drop your bombs or apply the gun. The thing is, when you're looking for AAA, and you spot a Shilka or SAM site, are you going to attack immediately as soon as you can, or are you going to build a comprehensive understanding of the situation?
When you are working with others in a multiplayer game or with JTAC or other allied support, you'll have a lot of assistance in building this information, but in this case, the challenge is in handling the situation alone with no support. Could you do it?
What I like to do is hold off my attack. I'll use my targeting pod and get a nice coordinate that I'd be happy to use for a firing solution, then I'll hit TMS right short to create a "markpoint". Markpoints are "disposable" coordinates stored in your CDU, sequentially labelled A through Y, with Z being automatically updated from your current position every time you fire a weapon. Every time you create a new markpoint, the next available ID in the sequence is used, so your first is A, then B, then C and so on. If you should hit Y, the sequence will start over, overwriting A and so forth.
When you've created a markpoint, your CDU will display its data. From here, you can copy that markpoint data into a mission waypoint. Waypoints are more permanent, and you can label them yourself so you can remember what that point represents. On the CDU when looking at a markpoint, one of the options on the right looks like a question mark next to a number, for instance ?8. When you hit that button, a new waypoint with the numeric id 8 will be created. The default name for this waypoint is MSN8, but you can change that easily by typing in a new name on your scratchpad (the keypad up front or on your lower right console) and hitting the button next to the existing name. Bam, you've created a new named waypoint from your markpoint.
(Sidenote, any field on any display with a pair of brackets  next to it is a field you can input your own data in via the scratchpad. Type something in, then hit the button next to the brackets.)
Now, by turning the left rotary below the CDU from "FLT. PLN" to "MSN" (the topmost position), you can cycle through your created waypoints just as easily as any other mission waypoint. Say you've spotted an artillery line. Create a mark point in their midst, save it to a waypoint, name it "Art". Spot a Shilka? Mark, save, label it "Shk1". Spot another? "Shk2". Now, when you're attacking just set your SPI to default to your current waypoint, cycle to the targets you want, and watch your TGP and Maverick automatically slew right onto the targets. From here on all you really have to do is walk down the list by priority. It takes so much work out of the moment, and gives you a clear perspective on the moving map as to where you are in relation to your targets.
Customising the MFDs
There are so many god damn options per MFD screen, but one of the built-in features of each MFD is changing what screen each button on the bottom row will take you to. To get to this screen, hold in one of the buttons for a second. This takes you to a blank screen with every possible MFD page listed on either side. Pick one, then push the button you want assigned to that page. Sometimes you will have to do this. For instance, say you take fire and lose your right MFD. If you want to look through your maverick seeker, you have to reconfigure the left MFD to display the MAV page. I typically sacrifice the status page first.
Get used to redundancy
The A-10 is kind of shockingly tough. It can take punishment that you wouldn't believe. I made a successful landing the other night without undercarriage. That said, things WILL stop working as you're taking fire. Coming out of a mission unscathed is a matter of both skill and luck; Sometimes you'll have failed to spot that BMP and take machine gun fire that somehow manage to take out your hydraulics. Maybe a tank manages to get some MG rounds on you before your bomb hits. It happens.
The good news here is that for every thing that might break, you're likely to have some system capable of filling in. With all the fancypants stuff you get through the moving map and TGP, it really helps to understand the more "boring" systems, such as the heading indicator (the compass circle below the artificial horizon sphere on your center dash). When you've lost your CICU and CDU, being lost without a way to navigate is a real pain.
Even better news is that it can be quite fun to fly this way. Flying mostly visually is a real challenge, but with some practise you feel like a real boss making your way home with no HUD and making a half-decent landing.
Bottom line though, is it can be real embarassing to only have lost your MFDs and feel incapable of making your way home. You can fly home and land just fine, but you have to challenge yourself to do it.
TGP and MAV slewing efficiency
This is an obvious one, but remember to zoom the TGP out when you want to slew faster, and zoom in when you want to slew with more precision. Conversely, slewing the Maverick seeker can be a real pita; You only have two degrees of "zoom" (in reality a wide angle and a tight angle), and the slew rate, while adjustible, is never perfect.
The trick here is to do all your slewing with the TGP, designating a SPI, and then slaving the maverick to the SPI. This lets you effectively target mavericks with the TGP, switch to the MAV page, then "poke" the mav seeker with TMS up short to make it lock on to whatever it's pointing at. The less you have to slew the maverick, the better, if you ask me.
This is probably a bad metaphor, but a lot of flying in DCS A-10 feels like doing halfpipes in Skate. I like to think of every dive as the start of a climb, so you need good speed on the way down, enough to maintain speed when you're going back up. In the same way, when you are turning, you are bleeding energy, which is unlikely to leave you with enough to make a good dive, which again is going to make climbing a pain. This is bad when that tank you missed is shooting at your ass.
I don't have any real "tips" here but I think it helps to keep this in mind,and try to keep a good speed at all times, around 200kts. Dropping below 180 at a low altitude is going to leave you very vulnerable. Practise turning without losing too much speed, and using energy from a dive to power a smooth climb. Flying will feel better, and you'll take less fire.
On the note of energy, flying with a full complement of ordnance and a full tank is a pain in the arse. For the sake of your own sanity, fly a little with no ordnance and little fuel: You'll be shocked at the difference. This is more impetus to use all your ordnance before returning to base, as landing lighter gives you more leeway as to your landing speed.