Reddit mentions of Pharmacy Technician Workbook and Certification Review (American Pharmacists Association Basic Pharmacy and Pharmacology Series) (APhA Basic Pharmacy and Pharmacology)

Not disagreeing with any of the suggestions here, but for a tech you do not really need a college course that is post algebra. I generally don't like to recommend biology, because in reality it is useless. Take an anatomy class instead. Physics and chemistry are take it or leave it options; I honestly don't believe they will help you as a tech.

Being a tech (and getting certified) is not hard. I started working as a tech in high school, registered with the board of pharmacy almost immediately once I started college and got my CPhT in freshman(?) year of college.

A lot of the stuff you do as a tech is unique and therefore will not be learned from a calculus course or gen bio/chem/physics. If you're dead set on taking courses, look online for some tech specific courses in your area. Otherwise, I'd recommend some of the books, as they are really great learning materials and prepared me superbly.

http://www.amazon.com/Technician-Certification-Pharmacists-Association-Pharmacology/dp/0895828294/ref=sr_1_36?ie=UTF8&qid=1376330318&sr=8-36&keywords=ptcb+books

and

http://www.amazon.com/Pharmacy-Technician-Certification-Quick-Study-Guide/dp/1582120986/ref=sr_1_52?ie=UTF8&qid=1376330338&sr=8-52&keywords=ptcb+books

were the two the I used, and I passed with a pretty high score.

I have this one in front of me, it's a decent reference and it's not very expensive. I used a different one to study for my CPhT, but I lent it to someone and can't remember the name of it. Really any basic pharmacy book should teach you the rudiments - SIG codes, pharmacy calculations/conversions, brand/generic names, basic drug indications.

Is there something in particular you're having difficulty with?