Read the book Code Complete. This explains a lot of ideas about how to structure code and the the reasons for doing so. Reading it should short-circuit your time to aquiring the experience necessary to tell good from bad.
http://www.amazon.com/Code-Complete-Practical-Handbook-Construction/dp/0735619670/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1229267173&sr=8-1
