It has just come to my attention that, sadly, the great site Chessville no longer exists. Fortunately the ARCHIVED VERSION is still available.
While there, you might want to take a look at the excellent article titled The White’s of Their Eyes, A Fresh Perspective on Mastering Tactics by Andy Hortillosa. It’s a three part article in which he discusses how to improve your tactical ability. His articles are based the theories of CJS Purdy.
From the Introduction: “Only a handful of chess authors truly understand the best method of mastering tactics. Most authors believe, as evidenced by the books and software available in the market, that puzzle exercises and solving them are the best approach to learning tactics. They could never be so wrong. The best way to learn tactics for most people is to actually learn them by seeing the transition point in its entirety from the opening phase to the beginning point of the puzzle.”
Another excellent article was Tom Rose’s Rose’s Rants where he detailed his attempt to gain the IM title.
There are also plenty of articles by many well known Masters and GMs.