Read some books about them first, look at some online stuff. It really pays to learn about a pet
before you buy it/adopt it. If a hamster doesn't seem like the pet for you, you shouldn't get one. A couple quick notes about them - yes, they are cute, but they aren't cuddly. They love to explore and even the most calm ones won't sit in your hands or lap for more than a minute. Second - hamsters sleep during the day. Since they aren't as active as a gerbil, they really should come out of thier cage for exercise every day. Hamsters are also rather stinky. They aren't without thier advantages though. My hamster, two years, died a while ago. (Hamsters usually only live two to three years.) He was extremely calm, wonderfully tame, and I really do think he loved me. Hamsters have a reputation for being "bitey", but Blacky never bit me, ever, ever. He was also extremely intelligent for a hamster. Most hamsters aren't like this though, sadly.
Could I recommend gerbils instead of a hamster? They live longer (three to five years) are awake during the day, don't need to be taken out to play as often as hamsters (although they do love it), and thier home needs cleaning only every two weeks. They are completely odorless animals, and tend to be more tame, smart, and affectionate than a hamster. They are also hilarious to watch. My gerbies will run on thier wheel, then dive through a few toys, and cling to the cage bars because they want to be taken out. They are also SO cute! They are brave, curious, cheap, and very easy to take care of. They are also loving and rewarding animals to keep. However, you MUST get two, since gerbils get lonely if they are kept alone. They sleep together, play fight, and groom another gerbil. (Be sure to read more about whatever animal you think you would rather get before you try to start to convince your mom.)