Brand/Generic/Indication for the most common drugs is all you need to know as a pharmacy tech. Lots of people will come in and say refill my blood pressure meds and you have to know that amlodipine is for blood pressure while their atorvastatin is for cholesterol. Or some people will only know brand name (ex. keppra) but since the pharmacy fills generic, you'll see the generic name. Some companies (like walgreens) have an easy database to look up brand/generic while I've heard that others (like CVS) do not. This really comes with time, though. Memorizing the top 200, though, is overkill.