I am little confused at what angle you should tap your left hand on fret board since your right hand would be busy in doing something else so our aim is that our left hand tapping should produce a clear note.
For normal playing your finger should be perpendicular and you should press the note on your tips of your nail . So while doing taping what position of fingers should be touching the note
Reference Video :
I using above video to learn that tapping technique.
That video isn't really a very good example of tapping, however the technique is the same as with any left hand tapping.
The ideal angle to hit the strings at is perpendicular to the fretboard, with enough force and accuracy to allow them to fret cleanly and allow a note to ring out.
An acoustic guitar may require a little more power than an electric, but good setup can help with this.
Check out this video of Joe Satriani playing Midnight, so you can see just how the fingers hit down on the strings. Be aware he uses compression and gain, a very low action, in order to minimise noise and amplify the notes played - you won't get that on an acoustic.
