The compressor is the heart of your practice. Clean dry air is vital to the proper performance of your equipment. As you all should know, your compressor is equipped with filters and dryers to help maintain the quality of your air, but contaminants can sometimes build up in an unexpected place: the storage tank of your compressor.
For this reason, it's a good idea to drain your compressor tank periodically. The frequency will depend on the age and condition of your compressor as well as the results of previous draining. Opening up the drain once a week is a good start. If you find the air mostly dry, you can then step back to monthly. For the first few times (at least) it's also a good idea to place a white towel (paper towel is fine) for the air to blow onto when it exits the drain. This will make it easier to see any contaminants in your air. In this context "contaminants" means things other than dry air. HOWEVER, contaminants in your tank can breed bacteria leading to bacterial contamination in the air too.
The photo below shows a compressor with an extension added to the drain to make it easier to access and drain. You can also purchase electric automatic drain valves to help simplify regularly draining your tank.