A string mute is almost always notated with an x. Several x's in a row, on adjacent strings, is used to notate a rake.
Right hand tapping (for right handed guitarists) is generally notated in tab via a t, in conjunction with the pull off and hammer on techniques used when executing right handed tapping. Thus, 2h5t12p5p2 represents traditional tapping technique.
When notating the tab for harmonics, the <> symbols are usually used, surrounding the fret which the harmonic is played at.
This should give you all you need to get started reading and writing guitar tablature. Again, if you're serious about music, it highly advisable that you learn standard notation as well as tablature. The excellent Modern Method for Guitar will get you sight reading almost immediately.
Okay, enough talk... time to get started learning beginner song tabs. Have fun!
