Read. A good start might be Bootleggers's "200 Proof Blackjack." Maybe follow that with "Blackjack Bluebook II" by Fred Renzey and "Blackbelt in Blackjack" by Arnold Snyder. After that, some heavier stuff like "Professional Blackjack" by Stanford Wong, "Blackjack Attack III" by Don Schlesinger and "Modern Blackjack, Volumes I & II" by Norm Wattenberger. These are just a few suggestions. There are many more.