Never memorize - this is how students get mixed up in pharmacology. Start by learning and remembering all the receptor subtypes and signal transduction pathways in the sympathetic and parasympathetic nervous systems; this is where many drugs work. Understand and remember the common places where drugs bind and the effect they have: on receptors, on enzymes, on transporters, on ion channels etc. Do the same for all the other receptors: for histamine, serotonin, dopamine, steroids etc. This way, you'll always know what the drug does in most tissues and you'll often be able to predict the side effects. Try to be systematic: learn and remember the receptor that the drug operates through, remember the post-receptor signal transduction pathway, and remember the common side effects for that drug class. This way, you'll understand and not have to rely on memory. Also, look for for common endings for drug names; this does not always work, but it will get you on track most times.
