Steaming is often the best cooking method that allows you to get the most nutrients while maintaining the food's natural flavor and texture. For proper steaming, the water should never touch the food. Although a lid will keep most of the moisture in the pot, when steaming for long periods of time it's a good idea to check, occasionally, that the water is not drying out.
If you are using bamboo steamers, keep separate steamers for foods that impart flavor to the fiber - one each for meats, fish, and veggies or grains.
To cook delicate foods, there's nothing quite as effective as a double boiler. It is also quite useful in warming food.
Generally, a double boiler consists of two pans; the lower pan, in which water is placed to simmer, and the upper pan, into which goes the food. Remember to use them on gentle-to-moderate heat.
When in a pinch, you can create a makeshift double boiler by placing a smaller pan (for the food) inside a larger one (for the water), and elevating the smaller pan with a trivet of some sort, to keep it from touching the hot bottom.