If you know how to read sheet music but your bandmates can only read tab, you'll need to be able to convert the sheet music to tab for them. Another reason you might need to perform this conversion is to teach someone (like a guitar student) how to read tab. Generally, reading tab is much easier to learn than reading sheet music, although you'll be a more well-rounded musician if you can do both.
Converting Sheet Music to Tab
Recognize the lines within the structure of tab. The bottom line represents the low E string; the rest of the lines going upward represent A, D, G, B and high E.
Recognize the numbers within the structure of tab. If you write a 3 on the bottom line, it means to play the low E string in the third fret (which would be a G note).
Transpose the melody line of the sheet music into tab. This can be used as a lead guitar part. For example, if you were to transpose the simple melody of "Amazing Grace" in the key of G to guitar tab, the first phrase would look like this: 0 (third line from the bottom), 0 (fourth line), 0 (fifth line), 0 (fourth line), 0 (fifth line), 2 (fourth line), 0 (fourth line), 2 (third line), 0 (third line).
Transpose the chords within the piece of sheet music into tab on another sheet of paper. This can be used for accompaniment. Do this by stacking numbers on top of each other. For instance, if there is an A chord, you would write a 3 on the second line from the bottom, a 3 on the third line, and a 3 on the fourth line. The bottom line and the top two lines would have zeros because they're open when you play an A chord. So you would have the following stack of numbers (from the bottom line going upward): 0 3 3 3 0 0.
Remember that tab doesn't convey note values (how long or short to hold notes), so you will need to play unfamiliar songs for your student or band members first so that they have an idea of how it should sound.