For me, milk has to be:
- high in calcium
- low calorie
- satisfying (higher protein helps)
I usually go with So Good soy milk because I like the texture and it's quite sweet, which appeals to me. I also like almond milk. Both options are excellent as far as the amount of calcium, protein and kilojoules per 100mL.
I have seen Rice Milk, Chia and Quinoa Milk, Coconut Milk and let's not forget the milk most of us know, plain old Cow's Milk.
If you have any diet intolerances (ie. lactose, gluten) start there. Look at the label - know what's in your milk! Compare products based on the quantity per 100mL rather than the "suggested serving size" which can differ markedly between packages. Here's a rundown of Calories/Fat/Protein and Calcium - the major factors on which to base your choice. From there, try different brands because So Good soy milk tastes very different to Vitasoy and everyone has a favourite.