Make flash cards. Basics on the flash cards, brand name, generic name, classification, action of drug, poss. interaction/side effects(the main ones),
common dosages, routes, I bought a packet of these and they were really handy, unfortunately I loaned them to a nursing student and never got them back but at the time I used them incessantly to study while in nursing school. You could make your own but it'd be time consuming. There again, writing it all down is also a great way to imprint it on your brain.
That is what worked for me. I think they were grouped according to drug class itself. All the cardiac drugs, all the diuretics, all the analgesics, etc.
Good luck! Hang in! You can do it Just purely memorization