I used a book to study for nclex called "pharmacology made insanely easy" by sylvia rayfield. She uses lots of mnemonics and pictures to help you learn and remember the different classes of drugs. I wish I would have had that book during nursing school. I did the sylvia rayfield nclex review 2 months before graduation. By that time we were done with classes and just doing senior clinical preceptorship. I had an excellent pharm teacher, who was actually a pharmacist and a nurse practitioner but that book would have help if I had known about it earlier.
As far as respiratory drugs go, they're all pretty much bronchodilators. We just finished respiratory in pharm. The trick that helps me remember the trade name and generic name is I try to associate one with the other (like aminophylline and theophylline-they're the phyilline twins lol)