When you're considering buying a piece of art, ask yourself this theoretical question: "How will it look in ten years?" You'll be surprised how powerful this question is when you ask yourself this many times. Many galleries have been known to generously offer collectors a certain amount of discount when asked about it by customers. But I think don't even ask, pay full price without thinking, and you'll get the best of the lot first.
Create a market, but do not blindly follow the market is full of sheep. Instead of focusing on what others have bought, go with your gut and be ready to talk to others about what you have bought. Spend money on one minor piece by a famous artist you've been following for a long time and five major pieces by artists who aren't that well known yet. The artists are gonna love it.
Ask around, talk to dealers, and vet them carefully. Find experienced, reputable dealers that you can draw on. A good dealer has contacts with local or national art dealer organizations. Find out who you like and work with them for a while. If a dealer sells you a way to avoid taxes, or suggests an artist change the color of a painting to match the curtains in your home, blacklist him. Collecting art can not only decorate your home, but also show your taste.