constant rereading in practice. For mechanics, a lot of the derivations of the formulas are geometric in nature. so drawing an ideal diagram helps with the derivations. However, depending at the level of the course and the demands of the course, it may be overkill.
I think its more important to know the statements, what are the conditions and under what cases they work, and what can they applied/used for.
What level classes are you at? intro? Junior? Senior?
Have a look at Alonso and Finn: Fundamental University Physics. Most things are derived and in general form. Not too many diagrams, but the diagrams that are in the book are memorable. Great and concise explanations.
if something more advanced, look at Taylor Mechanics. A bit more talkative, but Taylor does explain the why.
I did a dual major in math (pure)/physics, so I won't say much more. I will let more experience members chime in.