While rats come in a variety of colors and types, the most important characteristics to look for are personality and good health. All rats have their own personality and while most are outgoing and friendly if properly socialized before weaning, some can be shy, nervous, or independent. Rats that aren't afraid to nibble on your fingers or climb on your hand make the best companions. It's best to choose a rat 4-6 weeks old, but if your choice is limited to a shy baby, or an adolescent who begs to sit on your shoulder, choose the older rat. Any rat this sociable will make an excellent companion.
Males are larger than females when grown, and tend to be less active and therefore better lap pets.
Both sexes make affectionate pets. Whatever sex you choose, it's best to get at least two. Rats are very social and get lonely by themselves. As long as you spend time with each one, they will bond to you as well as to each other. If you get just one rat you must spend a lot of time playing with him.