If you have clients, they will tell you. If you do not, then the right thing is to follow your heart. To find a subject and to photograph it with feeling is like being in love -- with a thing, a person, or an idea (this love can also be shown tragically, through its absence).
Art, if it is anything above a technical exercise (which is also useful as a regimen), if a reflection of life. If you are honest with yourself about the things that are meaningful to you, you will find a way to chip away at them and explore them with the camera.
If the water still seems murky, it's time to just work on your chops -- you capacity to make meaningful pictures. Go outside and shoot passing cars and birds. Be rapid until your hands move without conscious planning. Perfect your usage of the meter, so that you do not need to use it. Find out how quickly you can be out the door to shoot. Do it at 6AM, at your front step. See where you go from there.