There's no harm in getting to know the market a bit by yourself, perhaps by visiting weekend open houses. In fact, it's a good idea to look at houses of all sizes and price ranges in and around your area to educate yourself about home values.
But this is different than actually shopping. (Try not to fall in love with a place that you visit during this phase!) You really should have your own real estate agent by your side for the offer and negotiation phase of buying a home. It normally doesn't cost you anything -- by tradition, the seller pays the commission -- and it's far better to have your own agent than to ask the agent selling the home to represent you along with the sellers. Such "dual agency" relationships often lead to conflicts of interest. For example, the agent might feel duty-bound to clue the sellers into the fact that you're actually willing to go higher on price.
Before you start seriously shopping for a house, give yourself time to ask friends and colleagues to recommend a real estate agent. Interview at least three agents, and choose one you feel will vigorously and professionally represent your interests. For more advice on this part of the process, see Nolo's article Choosing Your Real Estate Agent.