The sign LH indicates to hammer on from nowhere with your left hand fingers, and you just have to apply the same rules as you do for normal hammer ons. For those who didn't check out the last lesson, you just tap the string with your fingertip until the string hit's the fingerboard. It will provide enough force to make the note vibrate and therefore you get the note. Just make sure you hammer on on the fret shown after the sign. In a way, it's kinda like a right hand tap (using your middle finger to tap a note which I'll show another time) except on the left hand. Try this moving this excercise up and down the fingerboard, like so
C major excercise e b g d LH7h9h10 a LH7h8h10 e LH8 (tap onto the fret 8 with your index finger)h10
This will help all your fingers become strong and quick so that your hammer ons and pull offs will sound great. If you've checked other lessons on this site, apply this technique to other excercises on here. It's f--king tricky at first, but you can do it with patience. Last but not least, make sure you put these ideas into practise and properly. If you don't, you risk practising bad habit's in the future. Tricky techniques like this require patience and repetition, so you should at least do this kind of stuff for 10 minutes every day. It's not long, compared to how much Steve Vai used to practise everyday, and with each day you will notice an improvement if they are done properly. For now, I also suggest you keep the distortion as little as possible until you can do this cleanly. Sorry to nag at you but I'm just trying to help. All right that's it. Next lesson I'll help with right hand tapping. Keep shredding!
e b g d LH7h9h10p9 a LH8h9h11p9 e LH9h10h12p10p9 or how about this e b g d LH5h7h8p7p5 a LH5h6h8 LH8p6p5 e LH5h6h8 LH8p6p5