well, thanks a lot to you all
You just have to try it. Before my sweaters, I had only knitted 2 simple scarfs (I don't have a picture of them) and you can see how it turned out. Just find yourself a nice pattern and do exactely what's in the pattern. It'll work out that way.
Only problem is that it takes a LOT of time. (I've been working on my just finished vest since march this year)