i've almost entirely solved this problem for myself.
my rules:
1. say whatever you want and don't give a fvck what anyone else thinks
2. be yourself and if people don't like you for who you are, that's their problem i.e. fvck em
- says my cousin, the social god that he is (the loudest guy i know)
associate major Pleasure to GETTING ATTENTION and being LOUD
associate major Pain to staying quiet and not expressing your opinion and NOT getting attention
example: (ok, i had a couple of drinks in me first, but i wasn't even tipsy) walking down the town, shouting at fvck knows what, wearing my slash outfit (hat and wig); every girl that passed me stopped and talked (at least said "hey slash". the principle of associating pleasure with this attention held true and i LOVED the attention.
another example: me farmer dancing in a club (you're not meant to do this lol). everybody on that dance floor turned around and stared at me. i saw about 5 folk rolling their eyes. this was a little embarrassing, but it felt good, but i was being watched; i was the centre of attention - people were seeing that i was having fun.
it is almost a different skill talking in a large group compared with a group of two or three. feel the adrenaline when the attention is on you. people pay money to feel that (eg rollercoasters)
a role model helps immensely. imagine someone you know who is really loud and outspoken that you look up to and say "i wish i was like that". become that guy.
one more thing mentioned in tony robbins' awaken the giant within (p132 if you have it): do the most unpredictable thing you could do to interupt your pattern that you don't like. once you interupt that behaviour, your behaviour will already start to shift. the exam tony gives is if you're feeling depressed, look up to the sky, jump up and in the most idiotic of tones, shout "HALLELUJAH, my feet don't stink today". i can't remember, since i did this technique almost a year ago, but basically i just imagined feeling quiet and shy in a group and imagined shouting anything at the top of voice- i didn't actually do it, i just imagined doing it (i don't know if this was a good thing or not). eventually when the opportunity came to shout in public (fuelled by alcohol the first time, but not the others), i managed it, and it felt good - it felt like i had shifted my belief that i was shy in public to the belief that "i'm a fvcking idiot for thinking i was shy".
i managed to change myself for one week into this new mold, but reverted to my new behaviour (one of my role models turned out to be quiter than me :O, so i lowered it a little until the change disappeared). i'm sure if i wanted to, i could shift my beliefs again, and i'm sure you'll have no problem too.
cheers, gav