"Trading Up: Tips for Selling Your Home and Buying Another" featured on Nolo.com says,
"If you plan to sell your home and buy another, which should you do first? If you sell first, you’ll be under time pressure to find another house quickly -- and may end up settling for less than you wanted, or overpaying. But if you buy first, you'll have to scramble to sell your old house -- a particular problem if you need top dollar on your old house in order to make the down payment on the new one."
"Here are some ways to minimize the financial and psychological downsides of selling one house while buying another, read the entire article: "Trading Up: Tips for Selling Your Home and Buying Another"