Think of your family's lifestyle and how a pet will fit in. A dog demands a good deal of time, a cat less, and fish somewhat less than that. But all must have your time and attention to some degree. Match a pet to the members of your family's temperament. Keep the ages of children in mind.
Guinea pigs are good pets for younger children who want to handle the pet a lot.
Check the members of your family for allergies to animals. Sometimes allergies won't show up until you have a pet in the home. Its good to know before you take a pet home. Know who will be responsible for the pet before you adopt. Write down individual responsibilities.