IIRC, you have to read the naughty book at night, in your room, and then you'll gain enough points to start the waitress job.
If you haven't gotten the book, you need to visit the doctor at the Inn, eventually, a guy would want to sell you an erotic book. Buy it, read it at night and try going to the tavern (at night, again) to start the waitress job.
Oh, and when you already have the "Sell the paint" quest, remember to visit the top right part of the Inn during the day. I was stuck for ages on that one!
Game's good but needs a walkthrough or an in game way to track your quests.