does anyone have an idea of how to play touch harmonics? On my 'guitar techniques' guitar mag, it describes touch harmonics as 'a previously sounded note is touched above the fret marked TCH (e.g. TCH 9) to sound harmonic'.

For example it puts there as an example. for example you play an A on the 3rd string, 2nd fret (standard tuning), and you touch at the 9th fret, the harmonic given should sound like an E. but when i touch the 9th fret all i do is mute the string. and do i hold down the A and use my right hand to touch the indicated fret, or do i play the A, take my left hand off, and touch the 9th fret?

could someone also provide more details on this pls?
If you mean natural harmonics then you have to lift your finger off the string. If youre learning them its also a good idea to start at the 12th fret because thats where its the easiest to get them. Also, touch it above the fret bar and touch it gently because you're not trying to push it into the fret.

Theres a video lesson on the site all about this, check it out.

One time, after a gig, I had a foursome with these chicks that wouldn't shutup about my four-finger tapping.

I would much rather they had just talked about my penis.
It's not an easy technique to pull off that's for sure. Eddie Van Halen is known doing these, and as far as I can tell it helps...so at least you can hear it...to have a fair hit of distortion on whilst attempting them. Might also help having your guitar set to the bridge pickup, just so you can pick it up a more clearly.

So anyway, I find the best way I can pull them off is with using my middle finger on my right hand to tap on the specific fret bar, where you would normally play natural harmonics. The key is to hit it with a reasonable amount of speed so that your tapping finger doesn't actually pick the string. The quicker you can tap and pull your finger away the more likely you are to get the sound. Takes a fair bit of pratice, so don't expect to get it straight away. It's a matter of good timing and placement.

Good luck with it anyway!