This question was raised by one of the women in our group. (Did I get the question right?)
Here is one of my more recent attempts, specifically aimed at helping our children understand what we hope they will do when they babysit for us (and, hopefully, others). I get really excited about charts, and it is kind of the joke in our family. I word "rubric" especially fascinates me, so when I got to use it on a chart, BINGO! Made my day! :) My husband said he had to take this photo of me with my "Babysitting Olympics Payment Rubric" chart. (Thus my cheesy look.) (Subtitle on the chart is "AKA 'I get what I pay for' or 'You reap what you sow.' ").
Before we go on a date, I stick the chart on the fridge. Then when we get back, I discuss with the child who has babysat what he/she feels she earned. My goal is to have them decide what they have earned. I ask them what they did well first. They are usually quick to tell me what they didn't do as well, and usually I have to encourage them to be fair. I get the last word, but I try to be encouraging so that the whole experience is positive.
The plan is that they can babysit at the bronze, silver, or gold levels. I divided the areas of babysitting up into "events:" dinner, baths, bedtime, clean up. I described what I will pay per hour for that level of specific babysitting. For example, bronze dinner level says, "You let people get their own dinner, or you serve one item like cold cereal that doesn't satisfy. Children are hungry when Mom and Dad get home." Silver level says, "You serve more than just cold cereal, but it's not very appealing, and you let the children run off before they have eaten enough." Gold dinner level says, "You serve a real dinner: a main dish, two sides, a drink, maybe dessert! It is appealing and everyone is there and gets enough to eat." (Interpretation: they can use leftovers or make mac-n-cheese for a main dish, open/heat up a can of corn and cut up an apple).
One reason this is working so far is that my older children are motivated to earn money so that they can pay for their cell phones. Babysitting is a major earning venue. And they want to earn at the highest level possible in order to maximize their profits! (Better effort=higher wage=fewer working hours)