The most commonly available type of mouse is the domestic pet mouse. These pet mice have been selectively bred to improve the desirable qualities. There are also "fancy mice" (which are bred for show purposes, and come in a wide variety of coat colours), and spiny mice (which are desert creatures that are a bit trickier to care for) Usually when we are talking about mice we are generally referring to the domestic pet mouse.
Mice are often bundles of energy and activity.. They are not as social and interactive as rats and some of the other larger rodents, but they can become quite tame and allow themselves to be handled.
Although many people are squeamish about having mice in the house (simply because they are mice), mice are quite ideal as interesting pets, that are easy to care for and make very few demands on their owners.
Mice are nocturnal and very social. They will be most active in the evening and night, so don't expect to do much with them during the day. They are best kept in groups. A pair of females is the easiest, although larger groups are fine if you provide the cage space. Pairs of males should be avoided, unless they are litter mates, never separated, and given a large enough cage that they can have their own space (unfamiliar males are very likely to fight). Keeping males and females together should be avoided unless you want lots of mice in a short amount of time.
When picking out your mice, look for active bright mice, with smooth clean coats and pink clean skin on the ears and tail. The eyes and nose should be free of discharge, and the mouth and anal areas should be clean and dry. Their breathing will be relatively fast, but should not be laboured or noisy. Check the cage as well - it should be clean (the mice have been well cared for) and the droppings should be formed.
The size of the cage you will need depends on how many mice you will keep together. For a pair or small group of females, a 2 foot square cage is ample space. Mice will appreciate a cage with multiple levels as they do like to climb.
Glass aquariums, plastic cages, and wire cages can all work for mice. Aquariums will need a tight fitting mesh lid and lots of furnishing supplied for climbing and playing. It is also important to remember that ammonia and other fumes will build up faster in an aquarium or plastic sided cage than in a wire cage. However, as long as the lid is tight fitting they are pretty much escape proof, and have the added advantage of allowing a deep layer of bedding that the mice cannot spread all over your floor. The modular plastic cages meant for hamsters are actually well suited to the mouse size and temperament, but can be difficult to clean and some have poor ventilation. Wire cages (with horizontal bars) are nice because they provide lots of climbing opportunity on the sides of the cage, and it is easier to fix furnishings, platforms and toys to the sides of the cage. Wire cages marketed for mice are generally quite small, so larger hamster cages or even bird cages are preferable. Avoid using cages with wire mesh floors - solid flooring is a lot easier on the mice's feet.
The cage should be placed where the mice will have lots of human contact to make taming easier. It should be out of drafts, away from direct sunlight and out of reach of other household pets.
A nice layer of wood shavings or some other suitable substrate should be provided in the cage. The usual warning applies to avoid cedar and pine shavings due to the strong volatile oils released form these woods (especially cedar). Aspen or other hardwood shavings appear to be a better choice. Another alternative is paper or wood based cat litter - it is very absorbent and good at controlling odours.
Depending on the size of cage it may need to be cleaned quite frequently, especially glass or plastic sided cages that allow ammonia and odors to build up more quickly. It is best not to wait until you can smell a problem, because it will be quite overwhelming to the mice by then. However, the mice do mark their territory and if their cage is completely disinfected too frequently they may be distressed. A good compromise is to clean out half the shavings or litter at each cleaning, and only do a thorough scrubbing and disinfecting when absolutely necessary.