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One of the best classes I took way back in college covered SQL database design, and one of the best lessons from that class covered how to design relational database tables in 3rd or 4th Normal Form. So-called Normalized databases are key when storing data in a non-redundant manner.

Here's a little article that covers the normal forms and seems to represent them pretty well from what I remember.

Ah, after reading this, it even goes as far as mentioning Boyce-Codd normal form (BCNF) which is part of 3NF, and goes all the way to 5th Normal Form. I recall from my class that anything after 3NF was a little bit esoteric, but I'll give this a closer read when I get the time.

http://www.databasedev.co.uk/database_normalization_process.html