On an electric guitar, all the switches and knobs should work smoothly. This is the most important consideration. It's even more important than the guitar's sound. A guitar sounds different from behind than it does to your audience anyway. The thing you'll be most aware of is how it feels.
Different guitars have necks of varying widths.
Classical guitars have very wide necks. Electric guitars usually have narrow necks. Most steel-string guitars' necks are somewhere in between. If you have thick fingers, a wider neck will make it easier for you to play. If you have small hands, a narrow neck is more comfortable.