For the beinning and intermediate chess player, chess tactics should be the main emphasis of chess study. Spending time improving your tactical play will pay off immediately. Why is this? Because you will be able to spot tactical patterns more quickly and easily. Many more tactical opportunities will jump out at you during your games when you aren't evening trying to spot them! Not only will you become much quicker, but you're simply going to win more games - many times right in the opening.
Tactical play involves seeing ahead and spotting a play that will force your opponent to lose a pawn or piece or simply result in a positional disadvantage for your opponent. A great tactical player is more able to play brilliant games and sacrifices that result in wining positions or checkmate. Who doesn't love being able to play chess this way?
Here's how to improve your tactical chess play. Solve chess problems. Find 2 move, 3 move, and even for move checkmates to solve. Also find the 2, 3, and 4 move problems which simply involve gaining the winning advantage. There are plenty of books that cover chess tactics. I'm going to recommend and narrow down the field in a minute.
Another way to improve your tactical play is playing through games of famous players, especially a brilliant attacking player such as Mikhail Tal or Alexei Shirov. Mikhail Tal dazzle the chess world in 1960 with his brilliant style and becoming the youngest chess player at the time to be world champion.
Another great way to improve your tactical ability is by using chess software that's dedicated to solving chess problems. Chess Tactics Art 3.0 contains 1250 problems to solve covering tactical topics like breaking the defense, distraction, decoy, open attack, opening files, space clearance, etc. It's more advanced that a lot of tactics products. On the other hand a "complete" solution for chess tactics software is Chess Mentor. I think this one deserves a look.
Here are my chess tactics book recommendations. Chess: 5334 Problems brings the largest number of chess problems and patterns together in one huge volume. It's amazing. This book is praised by many coaches and teachers - they'll have their students solve 20 problems per day to stay sharp. Chess Tactics for the Tournament Player is more for intermediate and better players. GM Larry Evans calls the current book a highly instructive primer on tactics. It contains hundreds of strikingly beautiful positions arranged by difficulty and designed to sharpen tactical recognition and vision. Nothing is left to chance in this work. All materials have already shown their worth in Russian chess instruction.
For beginner's or students I highly recommend these two books. Chess Tactics for Students and Chess Tactics for Scholastic Players. Both are excellent for classroom or one-on-one instruction and follow a workbook format.
As always you'll want to spend time playing practice games and applying what you are learning. Play at your local chess club, or find an online chess play site like www.chessclub.com