You write a little story about your business and send it out to the media. You can't make it sound like an advertisement, you want it to sound like a news story. Think of an angle that would make your local paper want to run it in their business section.
Something like this:
The first night club catering exclusively to the under-18 crowd will be opening next week in Smallville. Located in the Westgate shopping center, Club OMG It's a Girl! will be the only club in Springfield County that is just for teens aged 14 to 17.
Club owner UTD89, 25, of Forest Hills said, "We are very excited to provide an alcohol-free place where teens can go on Thursday, Friday and Saturday evenings to hear the latest music, play video games, and socialize." UDT89 will offer free admission during the first week to any teen bringing a canned good to donate to the Smallville Food Bank.
etc. etc.