tactics trainer is good once you are an intermediate player. If you are a beginner, then any tactics book is ok. Even "Bobby Fischer Teaches Chess", overall a terrible book, is good for beginner tactics.
tactics!!

Read a good tactics book and understand all the stuff (forks, skewers, windmills, x-rays, etc.) Then to make sure u recognize these tactical opportunities, do lots of tactical puzzles. Chess Tactics Server is a good site for training your tactical pattern recognition.
A good book for tactics is the one in the Winning Chess series by Yasser Seirawan. It covers many different types of tactics and offers puzzles after each lesson.

I've read this book called "365 ways to checkmate" and it's improved my once very weak tactic skills. I now think more tactically after reading it then I used to. Try it, it's written by Joe Gallagher.

I recommend the book Back to Basics: Tactics. It had a very good review at ChessCafe.com and has a 5/5 rating at Amazon. I perused it at my local bookstore and think it'd be perfect for your level. It gives clear explanations of the tactical motifs.
I'm beyond the level that the book targets, but am thinking about purchasing the book anyway... it's just that good.
hi! im a 1200 player (internet) and people keep telling me to study tactics since i never did in my life. can anyone tell me a good tactics book for a player like me
and a good tactics drill book? also i would love it if you can tell me a way to increase my tactics/strategies skills. thank you!