Whats the best way to strengthen bones?

That depends on your opinion of "best". If you are deficient in calcium, the first thing to do is increase your calcium intake. That would be if you have trouble going to sleep, or if you seem to be unusually sensitive to pain. A specific exercise strengthens a specific bone. In general, you need to study some books about nutrition so you know how to eat right, Then study anatomy so you can plan an exercise program.