I'm getting the game friday, really excited to see what all the fuzz is about. 
Seeing as this is a very very unforgiving RPG, I'd like to ask the GB community for some spoiler-free tips. 
Anything I should be paying special attention to, that could ruin a playthrough? 
I don't have unlimited time to restart 2 or 3 times because I've made a fatal error.
 
Again, no spoilers please, I just want to get some starting tips.

Do not go for a Mage the first time. The Game is alot more fun with a Meele Character. Also I would look up a Character Build in the DS Wiki:
http://demonssouls.wikidot.com/
Otherwise play very carefully and use your Shield as much as possible. Also when you are gonna heal do it when far away from the enemy.
 That´s all for now and if you wanna know some more stuff I´ll gladly help you out.

Don't invest in luck, dexterity will help you in the long run. If you feel your not doing enough damage, light your sword on fire.
 
My spoiler-free advice

First time through, go with a Royal. 
You have a low Soul level, so it doesn't cost much to level up, a nice long range spell and a ring that refills your MP. 
Best thing to use to get used to the game..after that, its totally down to personal preference.

Give the Royalty class a shot to start. You start with a healing spell, but more importantly, it's the only class that starts with a ring that restores MP. Plus, the class is flexible enough that you can be pretty decent in both melee and magic, or you can specialize in one of them. 
 
But man, MP restoring and healing spells are a sweet combo.

" First time through, go with a Royal. You have a low Soul level, so it doesn't cost much to level up, a nice long range spell and a ring that refills your MP. Best thing to use to get used to the game..after that, its totally down to personal preference. "

There's a kind of huge thing you should know but it could be considered a spoiler.  But it is something that can mess up your game pretty bad, so:
 
 

Yeah..that's a good thing to remember.

hmm I bought the bought the game from america last December and played the shit out of it  but I am live in Iceland, do  you guys think I will be able to play with other EU ppl ?

fuck!  the title of this thread made me lose the game

I'm getting it on Friday also. I'm thinking of playing through it using Fist weapons only, is that even possible?

You  do know that you'll get a strategy guide with the game, right? I'm guessing that'll contain all sorts of neat advice on classes and stuff like that.

Been a while since I played DS. 
 
One thing that people tend to miss out on is the "story". Pay attention to all the clues. Each conversation contains information about the wolrd and how it ended up in its current state. 
Unlike other Japanese titles, DS wastes no words. The is NO exposition in this game. You really have to work for it.
And chances are it will only really open up to you after 2 or three playthroughs.
 
And oh, invest in a decent bow. Life saver in first playthrough.
If youre not a purist pump up Dex enough for it to do some damage. (chances are your first char wont be perfect anyways and you have a number of options to delevel in the game if you need to)

I'll happily start a new game with you-I'll probably be a Mage or something like that

I just got it this week dude! :D 
In Spain! Man I was so upset when this didn't come out in Europe when it first came out. So glad it finally came out in Europe. Man it's a tough game, but fair and good if you are cautious and respectful. It's what I expected and more, just love it.  

I started out as a Templar Knight, I just wanted someone that specialized in close range and had some guaranteed healing spells. Man the "something" Falchion +1 (sorry can't remember what it's called) and a healing spell I have at the moment are an awesome combo. I think I'm around level 34 or 36 at the moment.
Can't really give you advice, you're probably way further than me by now. But yeah, just thought I'd share the happiness :P

Royal is the easiest starting class, it does not get a healing spell though.  Spoiler free?  Learn to love your shield, do not mistake the game for diablo play the game like you would if you really were stuck in a crappy hell hole and everyone you met wanted to kill you.  That said learn to dodge because not getting hit is always better than getting hit even if you take no damage from it.  Do not read wiki's or strategy guides.  You will be a better player by learning the hard way.  Do not pump any stat until you experiment and decide what you really want to play.  Pumping dex is fine, if you love bows, don't plan to use much magic beyond defensive, and only like katana's, scimitars, and war scythes.  If you wanted to use something else though you just gimped yourself.  If you have to pump one stat pump vitality, being harder to kill is always good.  And did I mention don't read wiki's, especially ones about builds.  Learn the game yourself or you will be forever a newb no matter what weapon you have or how good your build is for it.