Final year finance student. Maths is a big part of my life.
Psychological tests have shown the answer to this: if you understand a type of mathematical equation, it goes into your long term memory. This is basically because if you know how it works, you only need to remember the underlying principles, and not a load of formulae, which is much harder to do.
In reality, the only way to make sure you get this going on is to ask a shitload of questions, until you get the teacher to either explain everything properly, or admit that they don't know. If they don't know, check out a library for a relevant book, and that book will know, as long as it's not pitched at school kids. Anything published by a university or a journal is worth having a look at.