Henry: We're up to four answers without a rant from the "I only represent buyers" crowd! How nice. The best thing to do, in my opinion, is to find a Realtor who "works" for you, understands your needs and knows the business and the area. Some realtors are very peppy but know little. You will be asked to sign a Buyer's agency contract with many. While this can be a binding nuisance, most realtors will allow escape from them, since there's nothing worse than a failed relationship (Ask Dear Abby!) Don't expect the escape to be Scot free if you just wandered off with another agent and bought a house, though.
If you sign a contract, be sure you know EXACTLY what it says and what the deal is all about.
Depending on the range of your search, you may find that you are looking beyond any one agent's scope. In that case, be honest with your now multiple agents. Let them know how you are working. You may find less enthusiasm but you will sleep better, knowing you did not mislead someone, expecting them to work very hard for no compensation. Realtors make no money at all if another agent sells you a house (unless they can enforce a contract that says that they will be paid if you buy ANY house. It is usually in a buyer's agency contract.)
And, in case you were wondering, I do not work with buyers without a contract. Been burned too often!