Understand the process:
Buying real estate is a complex matter and can be especially confusing for the first-time homebuyer. Do yourself a favor and learn as much about the process as you can before you begin. There are plenty of resources on the Internet, and most real estate offices will have pamphlets to explain things in plain language. You may also be able to research the real estate process by attending community-sponsored classes, or you can take a look at books like Home Buying For Dummies by Eric Tyson and Ray Brown, (IDG Books Worldwide, Inc.)
Use a REALTOR:
As a buyer, it usually costs nothing to hire a real estate professional to help you find and purchase a home--your Realtor will likely get a portion of the commission the seller pays to his Realtor. When choosing an agent, get referrals from friends, relatives, and co-workers, and then interview as many agents as possible. Pick an agent that works in the neighborhoods you're interested in. Listen to your agent, but make your own decision.
Don't buy your new home until you have sold your current home.
This is generally sound advice unless you live in an extremely hot market and your Realtor is sure you'll be able to sell your home quickly. Timing is crucial, so start working with your agent to find a new home as soon as yours is listed. With a little bit of luck, the day you accept an offer on your home, you'll be able to make an offer on a new home and close both deals on the same day. At worst, you may have to live in a rental for a couple of months, but most people agree that moving twice is preferable to being stuck with two mortgage payments!