Not much I can add to this excellent article:

10 Mistakes Buyers Make

Buying before selling is a classic real estate mistake. Avoiding it seems like the obvious thing to do, but who can resist – and who plans for – love at first sight? It happens, though, when buyers are just out scouting, fact-finding, and casually attending open houses. Then they stumble upon it: the light-filled house with a big kitchen and a fireplace, in their price range and ideal neighborhood. They haven’t even talked to a realtor about putting their own place up for sale. This is why bridge loans exist, they tell themselves. Our place will sell fast. The temptation is enormous.

Resist, experts say. Settle up with the old before welcoming the new, and watch out for these nine other mistakes even smart buyers sometimes make.

Complete article: 10 Mistakes Buyers Make - By Janice O'Leary, The Boston Globe