Make sure the camera you buy gives you quick access to different flash modes, including On (which forces the flash to fire even if the camera detects enough light--useful for back-lighting situations), Off (to prevent your flash from firing even in low-light situations), and Slow-Sync (which is also sometimes referred to as Nighttime mode). This last mode is particularly useful as it tells your camera to use a slow shutter speed in combination with the flash, thereby preventing background detail from getting washed out. If you don't find this mode in the Flash settings, take a look at the camera's preprogammed modes. Some cameras also include a nifty Flash Exposure Lock (FE Lock) feature. This lets you tell the camera what the most important aspect of the scene is and then provides just enough flash to illuminate it.
Autofocus: While shopping you'll read a lot about different autofocus systems. The most common thing you'll find is that some systems have more "points" than others. This simply means that they can detect a subject in more parts of the frame. More points are better, but the speed of the autofocus mechanism is equally important. Also, DSLRs don't have the shutter lag that many point and shoot cameras have. Still, focusing a DSLR requires pressing the shutter button halfway and can take varying amounts of time on different cameras. If you can get a hands-on experience with a DSLR before you buy, check the autofocus speed.
Continuous autofocus is a handy feature if you are photographing moving subjects. Some new DSLRs now offer continuous autofocus while shooting video. This is a great feature, but if you're shooting without an external microphone, your video might pick up the sounds of the lens refocusing.
Size: A full-size DSLR is larger and heavier than a point-and-shoot camera, so comfort is key. A camera that fits comfortably in one person's hand may be too large or small in someone else's. If size and weight are a serious concern, you may want to consider a compact interchangeable lens camera, which have bodies as small as point-and-shoot cameras.
Dust buster: If you think you'll be changing lenses often, look for a DSLR with an internal sensor cleaner. This helps keep your image sensor much cleaner, and dust free. If you're using your camera in rugged, outdoor conditions you may still need to manually clean your camera.