Can I drink alcohol whilst I'm dieting?

This isn't a regular occurrence; I like to go out, clubbing and partying with my friends (like every teenager does) but I'm on a diet, I'm eating healthily and doing at least an hour's walking everyday. But I want to go out at least once or twice a fortnight. I drink lager and spirits, and yes when I drink I like to get absolutely wasted!! What should I do? Advise please?...