One very common mistake made by home buyers is finding their agent by making sign calls. The sign in front of a listing has the name and number of the Listing Agent. These agents are under a contractual obligation to serve the interests of the Seller.
Calling them puts you about twenty years in the past when it comes to real estate practice in the state of Washington. In the bad old days before buyers agency, the agent who showed a buyer a home worked for the seller. This changed in the mid 1980s and now buyers agents are legally bound to serve the financial interests of a buyer in a home purchase.
So...if you are driving around looking at signs and you call the listing agent you are hurting your own interests in a transaction. The best they can do for you is be a dual agent. That is they can represent both sides in this purchase. However, when an agent represents both sides in a purchase they really represent neither side. Under Washington State law they are bound to avoid harming either parties interest in the transaction. This means that neither party could receive advice or guidence from the agent which might harm the other parties intersts. They become a glorified currier taking documents from one party to the other but unable to help either side make a good decision. (I can't really see why many seller's agree to this either. They need the advice about market conditions and the features of an individual offer as much as a buyer does.)
So what do you do as a buyer? You need to interview agents just like you would as a seller. As a seller you want an agent who gives you the confidence to know that you will be well taken care of after you sign a listing agreement. The same holds true for a buyers agent. You want to pick the agent that gives you confidence that they can do more than drive you around and look at the pretty counter tops in the kitchen. Pick the agent who shows that they understand negotiations and care about their responsibilities under the law. They are the ones who will serve you well.