These are the standards and anything else may not be around for much longer.
For connection to a computer USB 2.0 is the standard. Some digital video cameras use FireWire but those are becoming less common. For a direct TV connection S-video is used for all purposes on the high end and on the low end, though some cameras offer only standard A/V RCA connectors.
All viewfinders should be in colour and can range in size from 60 – 100 mm. Depending on how you use the camera the size of the viewfinder can be of varying significance. Viewing screen is also important. Most users prefer a larger screen, upwards of two inches, that flips out.
Other notable extras and features to take into consideration are battery life, charging time, and electronic adjustment