One of the first hygiene issues you'll encounter with your tween is when it's time to introduce deodorant. Body odor is just one of the many changes puberty brings, and fortunately, deodorant makes it less of a worry than some of the other changes your child will go through.
Be sure you talk about the different types of deodorant and help your child pick the one that works best for him. For some, aerosols are the best option. For others, gels or solids are the best choice.