Check for age group, this is especially important for some stuffed animals that appear to be for younger children, but have small parts that could be dangerous. Don't buy last years left overs, yes many of these toys may still be cool. Be careful of toys that will need additional items later. If the toy has a consumable item, add a few extras. Such as with Matel's fun flowers, buy some extra goop, or with a spin art kit, some extra paint.
Nothing is worse than half a toy.
Some things just don't stand alone. If you buy coloring books, you need to buy crayons. Batteries batteries and more batteries, most now come with expiration dates on them. Buy fresh, and buy extras.