Waitress Strategy

Not necessarily the most efficient, but a quite reliable strategy can be to focus on collecting Waitress cards.

In turn 1 you should hire a recruiting girl. Then you should focus on building up your structure and hiring more waitresses. If somebody else hires a waitress in turn 1, taking the milestone which increases waitress income, you should switch to a different strategy, since this milestone card is essential.

Having multiple waitresses is a safe strategy, because when the price war hits and people start aggressively dropping prices to ~$0, it's possible your waitresses is the only real source of income in the game. That however heavily depends on other player actions.