Young kittens need lots of attention and play to keep them busy. Because kittens have a great deal of energy, they need to work it off. Think of it as a three-year-old toddler racing around the house and getting into everything. The more things he has to do, the less he will climb walls and windows. An important thing to have is a set of shelves to help him look out the windows and race around the house without getting in the way or damaging anything. Cat condos with lots of busy things can also help, but the best play is when you dangle a feather on a string (or something else) and get him to chase it around the house.