start with natural harmonics - hit a normal fretted note, and touch the string over the pickups gently with a finger on your picking hand to get the harmonic. Once you get that, try getting the same effect with the side of your thumb as you pick (well, just after, but y'know).

It is easier to have someone show you, or to just figure it out yourself in my opinion... On the heavier strings the best points to get a ringing harmonic may be slightly different, and you need to dig in harder... :cool: