First, write your one notecards by hand, rather than relying on store-bought ones. The act of writing (not typing, writing) helps ingrain things in your memory.
Second, start with one piece of information at a time. Begin with the actions of all the muscles in a given compartment, then origins and insertions, and then the innervations.
Read your cards out loud. EVERY TIME. Quiz yourself out loud, too. Tape yourself reading your cards, then play it back to yourself in the car.
If you can, draw or trace and label the muscles yourself.
Make sure you're working by compartment, and not randomly, all over the whole body. Lots of times, muscles in a given compartment will share most of the same action and innervation, so that's half the information you don't need to learn from scratch!
If you need to review your bony landmarks to remember where the origins and insertions actually are, take the time to do so.
Pay attention to etymology. Lots of muscles tell you their origin and insertion (sternocleidomastoid) or action (flexor carpi ulnaris) in their names. When the former, the origin is always the first part of the name, and the insertion is always the second part.
Act out the actions while you study them. I'm constantly having to move my arms and legs in the middle of tests to remember exactly what the different muscles are doing.
That's what works for me! I'm starting my fifth quarter now, and I managed to pull through the muscles with a 98% this way. Muscles were by far the most difficult for me of everything so far, though! The concepts in other systems are more complicated, but the sheer amount of rote information to learn about the muscles felt very overwhelming.
Hope this helps!
Kat