Not sure of your budget but I'll see if I can make it kind of simple......
RAM is going to play a big part in the speed of your laptop. I wouldn't go less than 4 GB but it wouldn't be the end of the world if you had to go with 3. Don't go down to 2 or it'll be acting like your old laptop in no time.
Hard Drive is where you're storage space is. The bigger the better. If you shoot in RAW, you really need to go big. I shoot jpg and used 55 GB for 18,000 pictures. That's just part of the 220 GB's of data I have stored so far. You can never have TOO MUCH hard drive space. Also, the RPM's of a hard drive determine how fast you can access that data. i.e. 7200 RPM will be faster than 5400
Processors are all different and some people prefer Intel, some go AMD....blah blah.....again, not sure budget wise what you're looking at but I will say do not go with a Celeron or Atom at all. Even if it's free.
Card reader is a huge thing for me. I love being able to pop the camera card in and grab my pictures with no adapter.
USB and Firewire. what kind of devices do you have already? Make sure the laptop has what you need to use them.
Webcam. It's one of those things I've just recently started using. I just started using skype again and not talk face to face with relatives pretty regularly instead of just Thanksgiving.
DVD burner. Some of the less expensive laptops still have CD burners and DVD readers. Make sure it burns DVD's. It still reads and writes CD's also.
Video out. This can be a big thing or not. Most laptops have an output for an LCD monitor. A big plus would be an output for HDMI going to a HD TV. One of the things I'd REALLY like is the wireless connection for a TV.
Best Buy sells their Blue Line now which has it built into the laptops. Basically, you push a button on the laptop and it sends a signal to a small box plugged into your TV. My laptop is less than 1 yr old so I have to wait a while. The next one will have it.
Battery life. The longer the better. 6 hrs does not get you 6 hrs if you are actually using it.
Wifi. You probably can't buy a laptop without it but just double check.
Monitor size. I like the bigger style but if you're lugging it around all the time you may not want a heavier computer. I take mine everywhere and found that the 15.6" HD Widescreen was the perfect balance.
Weight. 2 pounds make a big difference.
Operating system. Windows, MAC, Linux........go with what you know.
I know I'm missing something but I haven't had a full cup of coffee yet.
