Yes - for instance, if you normally let the hearts empty out completely when they are a child, next time try keeping all the happy and hungry hearts totally full - or Hungry Hearts totally full, but Happy hearts 2 full, 2 empty.
Don't forget to let us know what you did different and which teen you got!
Yep! Feed it specific food, games, neglect it or not at all, leave it alone or always look after it, etc. You should get a different character. Though it is pretty weird having the same teen over and over. How many of them have you had in a row?