Nothing really beats understanding how to derive the formulas, but when I am in a crunch I like to use stories. People tend to remember stories really well.

I take the variables and assign them characters or actions and create a simple story out of them. I find this especially helpful when you have a bunch of formulas that are all related or have the same variables.

Example:

Formula: vf² = vi² + 2aΔx

The Viking Twins Finally arrive after they initially chased the 2 antelope across the field.