There are tons of resources online for FM...everything from tactics, to contracts, to training. The first place you might want to start is here:
Guide to Football Manager | FM 2013 Guide
Note the further reading sections at the bottom of each article...very helpful.
Keep in mind FM 14 is streamlining it's tactics creator to make it more realistic, so some of what you read in that section is already outdated. The BETA version for FM 14 is to be made available Thursday. It will only be available to those who pre-ordered...although yopu can pre-order at anytime up until release, and still receive the BETA version.