It really helps to have your intonation as close to daed on as possible.....and as andrew said works with the downstroke only unless you can hold the pick so that a lower finger can hit the string at the harmonic points on the upstroke.
There is a technique to it but one that you have to adapt to your liking....holding the pick a little deeper in your fingers than usual,or the same if you do this already,plucking the string with the pick and lightly nudging it with a finger and starting from above the
neck pickup area and going towards the bridge you can hear a lot of harmonic tones (octaves I believe) after getting used to the areas(practice.practice,practice) you can get killer pinch harmonics without a sweat.And you can do it with the chicken plucking technique also,where you use your thumb and whatever other finger you want(the index is my best)and plucking the same areas with a quick syncopated motion between the two fingers you can get good harmonics also,another one is to lightly flick the string, in the same manner as above,at the 12th fret above whatever the note is fretted at,if playing a hard E,fret any at the 15 fret.......it's all technique and with practice can throw a cool thing into your music....and
Billy Gibbons is the true king of pinch harmonics,ulnarian hit the outtro ont he nose,that is a classic of Billy's...whip out or borrow some older ZZ Top and you can here pinch harmonics in a lot of songs,pretty much using all the above mentioned techniques......