When I was looking for my digicam about a year ago, the two things I looked for were glass lenses, and optical zoom. Getting both of those on a camera with 2 megapixels is probably better than getting one without and 3 megapixels. Most cameras now have glass, but be aware that some don't.
Also, what kind of media does the camera you want have? that may be another consideration. Getting more cards/disks/sticks/etc. might be an issue, so price an expansion memory module at the same time so you know how much that will be. Keep in mind though, how many shots you will take. I have 32mb card for my 1.3mp camera, and I've filled it twice in one year, usually nowhere near that amount. A 3mp camera would benefit from a 64mb module, maybe even 128 depending on the number of pics you want to take.
Last, if you are looking for some special features like recording short movie clips, etc, that can limit your searches as well. Also check the ease of use of the camera yourself, don't trust others...find a working model you can play with for a few minutes and see how you like it.