You've already received some great advice. From a member's perspective, I'm one who tends to tip more frequently for things not on a menu than I do for menu items. I'll tip for something you did in the room that I thought was funny, interesting, or a tip note response to a comment/question. I'm very much an "in the mood" tipper so to speak.
Some menu items I do tip for are spanks, flashes (smile and boobs), song requests. Maybe some others if there's a poll or two. But, as mentioned the majority of my tipping is done for things not on the menu. However, create a menu that fits your personality and what you'd do so that members have an idea of things to tip for. The idea of something silly is a great idea, and I'll even say that I've tipped for a silly fact/item that a model has put in her profile.
Something that I haven't seen a model do recently is actively engage tippers to work the countdown. Something like "You know, favourite number is seven. Can I get seven tips of seven?" and you bat your eyelashes at the end of your request. Something that I enjoy doing is playing number games with a model. Not so much the token keno, though that could work too. What I'm referring to is over time I learned certain numbers a model might like, or not like. I'd tip odd amounts so the countdown lands in a specific number where it ends in a six (or 666/777) for example and they'd freak out about it. Or, tax season is another fun one because of Forms 1099 or 1040 (US models more specifically on these) when they have taxes heavily on their mind.
There's a number of different options, and ways to work the crowd. The key is finding what works for you to get them engaged and actively tipping.