I do not know about any specific meditation, however heavy weight lifting, such as power lifting greatly increases bone density and strength.
Saturn rules the bones in general, however I'm not certain how you could make use of that as I have never attempted to use saturnian energy in a magical working (safe for black magic), and generally a saturn square is not recommended as it often manifests with negative effects instead.
One thing to note about milk, processed milk if drank in excess can actually degenerate the bones and take calcium out of the bones instead, making them weaker as a result. Don't over consume it, or drink much of it, there are other good sources to get your calcium from.
Namely fermented dairy products such as yoghurt, kefir and things like goats cheese is also good.
Almonds are good too, they have a lot of other healthy nutrients in them as well, so they are good to add to your diet in general.
Maybe other people here with better knowledge on health and nutrition have other/better suggestions for calcium rich foods or bone enhancing foods.