The very first thing you need to do is to go to a reputable site. Like I said before, you can go to online bidding sites to try and save a bit of money. Ebay is the most obvious of them. The one thing I really like about Ebay, is the rating system the site employs after each transaction. Many of you already know this, but for those of you that don't, after each transaction the buyer and the seller rate each other's performance. So if you see a seller with a great reputation, chances are, you're not going to be ripped off. This is not to say that you can't get scammed, but the added tools of to rate sellers and buyers have reduced this very drastically.
If online bidding does not appeal to you, then fear not! There are a multitude of other sites for you to go to. Places such as Best Buy and Circuit City have their own websites for you to buy Digital Cameras online. The added bonus to these sites is that they're very professional and also usually come with some sort of a guarantee about your purchase. This also includes warranties and other things to make you feel more comfortable.
Another place that could be helpful are the digital camera forums that you can find. These places are just online meeting places that can help you out on a lot of issues including the best sites to buy from.
My best advice is to get on the Internet and search for "Digital Cameras." You will no doubt get many many many sites from which to buy. And for the bargain hunters this could be incentive enough.
Happy hunting for those Digital Cameras Online!