e |----5h7-------7p5-------|

okay try this to help you.. on the hi e string (the thinnest one) put your index finger on the 5th fret and play the string. have your ring finger hit the 7th fret (and remain there) so the note changes. to do a pull off keep your fingers in thsi current position (index finger on the fifth fret and ring on the 7th fret) and pluck the string. then pullyour ring finger off the string so that the 5th fret sounds.. .. if you do these to together you can get a trill (5h7p5). Hope this helps