Try to balance counting accurately and quickly. It's better to take a couple extra seconds than to wonder "Did that bottle of Gabapentin REALLY have 180 capsules in it?" With time you'll get faster. Also don't count on your hands. Ew.
Memorizing suffixes is 10x easier than memorizing every little brand/generic. (For instance, -olol is usually a beta blocker and they are usually indicated for heart conditions/hbp). Of course, you should do this to establish a foundation for memorizing the top 200, in the future.
Memorize the basic indications for the top 200, as well.
Put X's on open stock bottles (it really depends if your other techs do this, it makes everyone's lives easier if they do)
Insulin is always in the fridge, and the fridge should always be between 36*F and 46*F (you probably wont need to know that last one, but I like to check the temp occasionally to prevent us from magically losing all of our stock haha)
If your store is slow, like mine, there will be times when there isn't much to do. Just be on the lookout always for anything that can be done/tidied up/organized (within reason).
Most importantly, just be observant. Experience is the best instructor. Take notes if you have to. And best of luck to you!