how to convince a parent to give you booze for a party?

Tell him he'd not only be breaking the law but, should any of those people he helped get drunk end up getting into a horrific drunk-driving car accident, he'd also be in danger of having someone sue the pants off him. That should work like a charm!

start drinking eratically, wait outside liquor stores to get people to buy your booze start drinking constantly, getting picked up by the cops once or twice a mnth. works really well. Before long your folks will insist if your gonna drink they insist you do it under there roof so they can keep an eye on you. See easy worked for me at 11yrs old.

I'll assume you are underage because if you weren't you could buy your own without any reference to a parent. Having a drink in his presence is one thing. It may be quite legal where you live and even if it isn't it's acceptable as far as many people are concerned. Supplying you with a bottle of something and you taking it elsewhere to consume, unsupervised by your dad or even anyone responsible, is a whole other story.