Step 1: Find a surface to tap. Ideally, a large, flat one. A desk, a table, or a friend's forehead will do.
Step 2: Position your tapping hand correctly. Make sure it's at a 45-degree angle and your wrist is cocked just so.
Step 3: Tap with precision and finesse. Think of it as a delicate piano performance, minus the piano.
And for the love of all things sane, do not tap the eyes of your coworkers.
Tapping your own forehead is also acceptable, but be prepared for a lifetime of existential questioning.