In response to a question on the Forums, here's one way to convert 6 string tabs into 3 string, tuned to a dyad chord, also called 1-5-1, "power chord" or perfect fifth.  (For example, tuned GDG)

Before you start

1. This is likely to do your head in until you get to the example, then it'll be easy
2. Do the example with your guitar in your hands

Figure out the key of the original

Most songs start and finish on the tonic chord so if the first and last chords are E for example then it's safe to say that it's in E. If they don't go with the last chord.

That'll usually do it, if you're still not sure look for other chords in the song. I IV and V chords are common in most songs if you're not sure but think it might be in E, see if there are plenty of A and B chords (count the 4th and 5th up from E, starting again when you get to G)

Find the first note of the riff or melody on the 6 string tab.

Find a 6 string fretboard map online somewhere and get the name of that first note. Count up from your tonic (the name of the key) until you get that note so that you know what number it is. For example if we're in the key of E and the note is B you count up E F G A B and the number is 5

Figure out the rest of the notes on that string

The rest of the notes on that string will have the same relationship to that first one so just count up your frets. For example the first note in the original is on fret 2, the second is on fret 4 and the third on fret 5. Now you've found that the first note is a 5 and on the open position of the middle string, find the second note by adding 2 and the third note by adding another 1.

Repeat and rinse

Do the same thing for every string on the original tab.

IMPORTANT

Do this with simple songs to start with

Satisfaction

6 string TAB

E-|-----------------------------------------------------------|
B-|-----------------------------------------------------------|
G-|-----------------------------------------------------------|
D-|-----------------------------------------------------------|
A-|-2--2----2--4--5----5--5--4--2--2--------------------|
E-|-----------------------------------------------------------|

1. The song is in the key of E, that's obvious from the chords
2. The first note in the tab is a B which is the 5th note up from E
3. The 5 on your 3 string is the open position middle string
4. The next note is on the 4th fret, 2 up from the 2nd, so our next note is 2 up from the open middle string, on the 2nd fret
5. The next note is on the 5th fret so ours is up one more from that on the 3rd fret.

Your tab looks like this

G-|-----------------------------------------------------------|
D-|-0--0----0--2--3----3--3--2--0--0-------------------|
G-|-----------------------------------------------------------|