Try and control how much you pull off. You could pull off earlier instead of dragging the string with your finger by accident. Another example would be
e 5p0 7p0 8p0 7po b 5p0 6p0 8p0 g d a e
This shows how you can mix hammer ons and pull offs together. It shows how important it is to make them loud otherwise the notes will fade out (unless you're using loads of distortion. Here's an example from one of my own solos
e 8p5p0h8p5p0h8p5p0h4h7p0h4h7p0 b
This includes a pull off from the 4th finger to the 3rd on the last phrase which is quite tricky. Be sure to practise before playing the whole lick. Even Kurt Cobain used them and he wasn't one of the most proficient players around. Here's the main riff from 'Man who sold the world'
e 12 b 15p12 12 15p12 17p12 14 g 15 15p14p12 d 14 a e
This would make a great excercise if you moved it by one fret each time until you reached the twelth fret. Other Examples You might want to listen and check tabs to the following songs 'Battery' by Metallica, Anything by Alterbridge They also use hammer ons from nowhere. 'Crush day' by Joe Satriani. 'Whiskey in a jar' by the one and only Thin Lizzy. Also check other lessons on the website for excercises. They really do help! O.K. my work is done. Please post any comments if you'd like to tell me what technique I should write about next which you need help with.
e b g 2 2 2 0 2p3p2p0