To maximise the non buying method, on arrival to the pub, make sure you hold the door open for your mates to enter in first. The rest should take care of itself.
I can probably say this as he's not on here, but my drummer in the band is a tight bugger. (perhaps Animal can verify this is a drummer's trait?)
At gigs, after we've finsished playing, we head to the bar. I don't drink btw, but I found that I was putting my hand in my pocket first - He would just stand there and verbally issue his prefered beverage - the rest of us would be thinking "yeah...but who's going to fund this?"
Anyway, to be fair to him, he's developed this method over the last 12 years or so.
These days though, I just order mine or say "get your money out guys" It's a bit w@nky, but I just don't care anymore.