I played this game a bit in the past (I think I got stuck at some point, can't remember exactly why I stopped).
Anyway, this time I want to beat it.
Now I'll create a new character, but don't know where to start.
Can I make a evil dude?
What build would be reccomended to me? Warrior, archer, etc.
Should I play in easiest difficulty mode?
You know any walkthrought/guide (for the case I get stuck) ?
Hmm that's all, I think. ^ . ^ '

This is true. In fact, most of the best NPCs in the game are evil. Just make sure your reputation doesn't go too high. Evil characters don't exactly like to be seen as heroes of the land. ;)

I forgot to answer this earlier. I would pick whatever you find most appealing. Since you can have other npc's join your party, you can fill out the other combat roles with npc's. Baldur's Gate is really good at making all classes very playable.

Also, if you own Baldur's Gate 1 and 2, I highly recommend trying out "Baldur's Gate Trilogy" (often called "BGT"). Here's a link to the readme: http://www.spellholdstudios.net/readme/BGTReadme.htm

It fuses the games into one big game and as an added bonus you have all of the classes and features from BG2 available in BG1.

Thanks! I installed this already. It's mandatory for the ultimate experience. : )

Dan Simpson's walkthrough on Gamefaqs is excellent. I recommend that one if you're still looking for a good walkthrough.

You could also check out sorcerers.net for some more guides. They have quite a few good ones.