If you're lucky enough to be able to sit in a class taking notes and basically "get" the course material, when it comes to studying the necessary formulas, there's a quick and easy study tactic that requires about a single hour prior to testing. Basically, condense all your notes [formulas only, or concise examples] into a single page front [maybe back] and then read the page--over and over until the class starts. Receive the exam, flip over to the back page or ask for note paper [assuming they provide it] and regurgitate what you read back on to the paper. It takes about ten minutes. Then, take the test, referencing your notes as needed. I like to call it memory dumping, I've known lots of people who do similar but have there own names for it.
The crux of this tactic is that you actually understand how to apply formulas, so it of course presupposes you know the material.
I made condensed notes for a few courses, but the act of creating them was key, not the resulting few sheets of paper. I wouldn't write any results down until I could derive them myself (within reason). And writing them by hand, rather than typing/latex. Somehow, I can understand something much better if I'm reading my own script than a print-out, even if the content is identical.
When giving a written test on some theory subject, I sometimes let students take in their own hand-written notes on one side of an A5-sized piece of paper, then hand it in with their test. If students are going to sneak in a piece of paper stuck up their sleeve, then why not let them all?
The crux of this tactic is that you actually understand how to apply formulas, so it of course presupposes you know the material.