One of the first things a doctor usually tells you when you are at risk for bone loss is to make sure you are getting enough calcium. Calcium is important to building and maintaining bones, but simply increasing the calcium in your diet often is not enough to build stronger bones.
Most sources I've read agree that several other elements are needed to absorb and use calcium:
Magnesium (citrate for better absorption)
Boron (in some multivitamins)
Vitamin K (a good source is alfalfa)
And doctors now are saying that at least half of the calcium we take should come from our food, rather than supplements.
One of my favorite calcium-rich breakfast foods is a smoothie made with kefir (it's like drinkable yogurt, high in calcium and high in probiotics and is supposed to be easily digested). You can add strawberries, peaches, blueberries, ground flaxseed, protein powder, and even spinach or other greens. And you don't taste the spinach!
To sum it up for today: a good diet is a good start, but must be combined with weight bearing exercise to stimulate bone growth.