Trying to clear things up a bit:
Hammer ons should be clear to everyone.
Pull/Flick offs:
They are not called "Lift offs" for a reason: just try it! Play a fretted note, then (slowly) lift off your finger: the resulting sound will be muted a little (even if you do this fast) compared to the previous fretted note.
Therefore, you need to "pluck" the string using the finger that pulls off. What you want to achieve is that the note after the pull off has about the same volume as the one before the volume. There are two possibilities to do so:
1) just pull your finger downwards, towards the ground and let it land on the next thinner string (and thereby muting that lower string).
2) pull diagonally down and away from the fretboard, thereby gaining a little distance between your finger and the fretboard.
Which one of the above methods you need also depends upon the circumstances (song, speed, effect you want to achieve). Also, the simple "lift off" method can come in handy when you need to play very fast thrills and the equal volume across the notes isn't that central.