In the grocery store you will often find tempeh that says "pre-cooked" and "ready to eat" on the package. Even though it's fine to eat this tempeh "as is," you might still want to steam this tempeh for a several minutes if you enjoy a tempeh that is a little softer. Pre-cooked tempeh that is steamed just before its addition to a recipe can sometimes do a better job soaking up recipe flavors as well.
Since tempeh can be cut into slices or crumbled, you can control the degree to which you would like your tempeh to be "recognized" in whatever dish you are preparing. Crumbled tempeh will usually be much less "evident" as similar to ground meat it will shift into the background of the dish and feel much more like a texture-only component. Sliced tempeh will usually be much more "evident" and will feel like a more "featured" ingredient of the dish. Both sliced and crushed tempeh can still do a great job soaking in flavors and sauces.