Just as birds, bees, and butterflies need the proper habitat in order to stay in the garden, so do beneficial insects. In addition to bad bugs and nectar-producing plants, shelter and a good water source are important. You can construct bughouses for beneficial insects; however, they are not necessary. Tall grass, thick shrubs, and lush foliage make the perfect hiding places.
Beneficial insects also need a source of shallow water. This can be as simple as a small dish or a birdbath with a few rocks in it. Keep in mind that if the water is too deep, the insects may drown. Change the water every couple of days to avoid mosquitoes and to give the good insects a fresh drink.
If you use mulch, leave a few areas of the garden uncovered, as there are many minerals in the bare soil that insects need for their health. If possible, create small areas of bare soil that will puddle (just remember to keep them as shallow as possible). An easy way to do this is to make some small holes that water can puddle in the soil below a hummingbird mister.