Before you choose your hamster, always make sure that the pet shop, farm, or person that you are getting it from has treated the hamster properly and that it is not sick or suffering from malnutrition or other problems.
Do make the time to interact with and handle the hamster before you decide on getting it. This allows you to be sure that you can take care of the hamster and are comfortable with it and its personality. This also gives the hamster a chance to get to know you.
Commit to a hamster (or hamsters) only when you are sure that you can handle it (them).