I had a great time playing the demo today, but you should follow the following guidelines for the best Battlefield experience.
 
Squad up. Invite 3 friends who you know well, and work well with.
 
Stay together. You loose the whole point of the squad if you scatter yourself among the map. 
 
Use mics. Communicate the location of enemies, armor, or your current health or ammo state.
 
Coordinate your attacks. Use the last three steps to maintain a strong defensive or offensive advantage over the other team. You are only 4 people, so don't try to defend both crates, you will only over-spread your resources and lose both. Pick a crate to attack/defend, and don't abandon the plan unless everyone is aware that the target has been changed. 
 
Mix up the classes. If everyone goes engineer you won't have a very good balance. If you are attacking I highly recommend rolling with two medics, they are great for giving out health and mid-range combat, but their true skill is zapping squadmates back to life, it will keep everyone together, and you won't lose tickets.
 
Me and my friends have a blast with this game, and if you follow these steps, I can assure that you will too.

Seems like every online game should be played like that. I had a blast with the game today playing with randoms, but I can't even begin to imagine how fun it would be with friends. 
 
Also, if you snipe, screw you.

How to play Bad Company? 
 
Blow stuff up.

I agree with you on this. It helps so much sticking in a squad, and playing together in a squad is totally awesome and very rewarding.
 
I find myself winning more matches and having more fun working as a team with my friends.

Your suggestions should be the golden rules to play by. If you get a working squad, you WILL decimate all provided the rest of your team is not clueless.
Couple things to add:
-keep an eye on who's left in your squad, if it's just you, you should probly hide and wait the 10 seconds for your buddies to respawn on you back to full force rather than have everyone die and have to spawn at base.  Sadly this happens all the time with randoms where they don't wait and you spawn at the back or on a sniper revealing his position.
 
-Attack the F-ing crates! All too often people get caught up on killing the opposing team. If you're attacking, all you're doing is losing tickets. Remember to push crates at all times.
 
-last but not least, there's no need for 10 snipers on attack. 2-3 snipers should be able to hold people off stationary equipment and keep the other snipers at bay. Everyone else should be hitting crates/flanking.
 
I was playing with one other buddy in my squad  last night and we absolutely wrecked house cuz we stuck to Jayross' rules and our own. Blew up close to half the points, just the two of us. *cue Will Smith

Yeah this game is at its best when you have a decent squad, I played with a friend and had a good time over the weekend too bad i forgot to take a mic.
 
Im trying to keep away from the demo, it keeps calling to me but I want to go into it as fresh as possible now I know how awesome it feels.

" Seems like every online game should be played like that. I had a blast with the game today playing with randoms, but I can't even begin to imagine how fun it would be with friends.  Also, if you snipe, screw you. "

" How to play Bad Company?  Blow stuff up. "

" @immike: Speaking of spotting and or marking targets; more people need to use that shit. Its amazing really, it makes it so much easier to kill things when you know there's a few baddies within your vision by just smashing the back button.  I totally always spot targets so my team can light them up. "

sadly all my friends rather play MW2 then BC2 with me. dont get me wrong. MW2 is great and all, its just i want something different

This might be a really dumb question, but, how do you unlock the UAV for use the demo? 
 
I agree with the OP completely. If you role with a squad of friends you are bound to have a lot more fun. It really is a blast.

If you have C4 when planting the crate charge, put it on the crate also. Then either hide and blow it up when they try to defuse it or if they're going to kill you before you can hide, blow the C4 even if you're in range. Don't let your C4 planting be in vain.
 
If you see a buddy drop C4 on the enemy crate and die before blowing it, shoot the C4 to detonate it yourself. I think it takes 9 to 12 C4 to blow a crate in the demo. 5 to 6 for the PC beta.
 
Equip the shotgun to the assault class so you can use the C4 with his ammo box. This way you can C4 crates all by yourself if you're stealthy enough.

Im really gutted i dont have any friends that play Bad Company, maybe when the game comes out i might look at getting into forums/clans to actually play with people i can work together with and not random people. Even by my self this game is a blast! I havnt played Modern Warfare 2 since the demo came out! Bad Company is way better!

I haven't had many friends playing, but I've found that I can usually squad up with one or two decent players and they'll spawn on me when I do my little flanking actions. It seems like if you take the offensive really early on the flanks, it's easy to get the plant and get an angle to keep it planted, since defensively people are really slow to set-up. 
 
Still, sounds like it would be much more fun with friends.

I know I used to play a lot of BC1, and wanted to find some people to play with who were a tad more serious.
 
Now I'm in Tactical Gaming / Tactical Warfare  http://tghq.org/
 
The people there are really cool, and it doesn't require that much of a commitment of you, we have mandatory practices on Wednesday at 8:00pm EST and Sunday 8:00 pm EST. If you can't make the practice for any reason all you have to do is send your squad leader a PM.
 
They have divisions for Battlefield, Call of Duty, Endwar, Halo, Killzone, MAG, etc.
 
Anyone can PM me if they have any questions, I would be glad to help.

@Jayross:  That group sounds pretty cool, but it'd be so hard for me to guarantee a night every week for practice.  Not to mention I'm all consoles now.  If you or anyone want to form a squad casually though, I'm totally down for that. And the demo is a good way to try out teammates.  I'm on 360 though, GT= Im Tom Jane, anyone who wants to play, feel free to add me

They aren't really hardcore, I thought it would be something like that, but everyone is just really friendly and works as a team. If you want to get an idea of what they are like, there are rules for no spawncamping, cheating, or even cursing.