No worries BBJ 
And Bluesbreaker you are talking about natural harmonics. The easiest ones occur at the 5th, 7th and 12th fret.
You can hit others, the 3rd fret and 4th are quite good for metal. If you have an electric with a whammy bar try the G string at the 2nd fret with the gain cranked to get the Dimebag Divebomb.
Also don't forget that past the 12th fret the pattern repeats again, so you can hit harmonics right the way up to the bridge i.e the classic Jimmy Page riff.
Best tip i can give i guess is to practice on an acoustic, get quite a firm contact on the strings. Don't push them down but don't feather them either and give the strings a fair old whack. Eventually you'll find the sweet spot, then just refine it down on electric.
Job done!
Another fun trick with harmonics is to kinda reverse it, so for example on the D string fret at the 5th and hammer on the 7th repeatedly as fast as u can. Whilst doing that run the edge of your picking hand down the strings towards your other hand, start between your pickups, as if playing harmonics then move back towards the bridge. Gary Moore eat your heart out.
Huh.. turns out I had more to say than I thought!