I talked to several people at PAX East who asked, "How do I start building?"
When I first started playing Mechaton -- yes, Mechaton, I've been around that long :-) -- I started by buying a couple of sets and a bunch of bricks from the Pick-A-Brick wall and putting together some stuff that I thought looked neat. Then I started copying things that I found instructions for online. Then I just copied things I saw online. Then I started dumping pieces from sets out in a big pile and trying random connections while sorting. Occasionally I pick a random piece and try to build a mech around it, or using it somewhere in the build.
If you're new to building things with Lego, don't be afraid of building simple things and discovering how the pieces connect. Appreciate the things you see online from experienced builders but don't be intimidated. Everyone had to start somewhere. Just like any other skill Lego building improves with experience. You build a library of techniques over time. Keep building. Do it as much as you can. Practice makes perfect.
Just Build It!