I would suggest some of Jeremy Silman's books, and Chess.com's tactics trainer. 
Tactics
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Aug 15, 2009
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#2
For tactics, Chess Tempo is superb (and completely free).
I would suggest Ward Farnsworth's Predator at the Chessboard, available online at www.chesstactics.org. As a fellow beginner, I found I learned more from thorough explanations and puzzles sorted by each tactic, than by just solving a bunch of random puzzles.
As a beginning player, I am told it is best to study tactics or endgames first in order to improve quickly. Can anyone recommend which they think would be best to study first as well as a good book in each category for someone just at the border between beginner and intermediate?