i wouldn't call it a how to, just more of a definition. to be honest, sucking balls is pretty common sense. there's really only 2 main rules: don't suck really hard, and don't bite even remotely hard. they're uber sensitive. basically, if you have to ask 'how' i think there's an issue, because you just sort of do it... of course there's a few neat tricks you can do though.
i should do a 'how to' for a few things you guys might just be interested in... haha jk