Here are the choices and tradeoffs:
While it may be the most expensive option, a good store with trustworthy staff can help you find the right camera for your needs and keep you from making a mistake. There are also local stores whose staff are ill-informed, misleading, and more interested in a profit than in your needs, but they do not last long in these days when online stores are so accessible.
Ask your photographer friends for a good recommendation.
Discount retailers such as Circuit City, Best Buy, CompUSA, and Walmart offer good prices, especially if you can catch a promotion or sale. Be skeptical of any advice they offer. Sometimes they get good sales people, but just as often the people are learning on the job. Do your homework and trust yourself when going here. Do NOT buy camera memory here. It is much cheaper on the web.
The best buys are usually online, especially for camera memory. But some offers are too good to be true.
How do you know which to patronize and which to avoid?
The most reputable camera store on the web is http://www.bhphotovideo.com. This New York camera store has a great reputation on and off the web. (Most NY and NJ discount camera stores have poor reputations.) Another store that generally has among the best legitimate prices is dbuys.com. I have heard good things about this outfit.
Pricegrabber.com is perhaps the best price comparison site. It combines the price comparisons with the vendor ratings. Never buy from a vendor that you don't know unless it has a very high vendor rating. For more vendor ratings, see http://www.resellerratings.com/.