\documentclass{article} change text width

Question

The default margins of this document class are too big, or the textwidth is not wide enough by default. I prefer having ~80 char per line.

I really don't know how to widen this.

Which command and how to use preferably in my case?

I guess it's a simple thing to do, I'm just still very ignorant with regards to tex stuff...

edit: I first tried \setwidth but it unbalanced my margins left and right. geometry does the better job, I use the width option there.

Thanks!