How to Brew is indeed a good site, and has a lot of useful and nice-to-know
information. However if you start brewing the way most people do, which is by
making beer from hopped malt extract (a.k.a. beer kit), there's one thing you
should remember: do not boil the extract. If you do, you're simply making extra
work that will do no good for your beer (actually it'll probably make it worse).
But don't take just my word for it, check out these sites for example: