Tapping isn't a common technique but it will help you do the following:
- Strengthen your hands, wrists, and fingers
- Increase coordination between the hands
- Tighten your rhythms
- Gain accuracy and fluency
Besides, it's great fun!
You need to know how to play hammer-ons, pull-offs, and slides. If you're not sure, check out this lesson: Bass Guitar: Hammer Ons, Pull Offs, Ghost Notes, String Bends, Slides and Vibrato
You also need to use your (dreaded for some) little finger. This exercise will help: EASY But Effective Bass Exercise (Technique/Speed/Accuracy/Stamina/Memorisation)
To dig deeper into technique, I recommend my book Creative Bass Technique Exercises:
Billy Sheehan Bass Tapping
Billy is probably the most famous bass 'tapper'. Look at this!