My students can invert function and tell me for which values of x a geometric series converges, yet they can't do squat with fractions. It's not for lack of "teaching for understanding" - I made sure every step of the way was solid when we did fractions last year. But since then lack of practice and reflection has pushed the understanding and skills far back into awkward recesses of their long-term memory (at best!).
So I've been searching for a good mnemonic, and haven't found anything that covers the whole topic. In high school, I too had trouble remembering the rules and often used the 1/2 fraction to remember. This week, I saw a student use it the same way I used to, without me or anyone else having shown him, and so I decided that together he and I could introduce this method to the rest of the class.
Here is the worksheet I've designed. Google Docs mangles equations, so download the file for best effect. Please offer suggestions for improvement. I'll hand this out to the class on Monday.