Warning of the Surgeon General
Chess Tactics Server (CTS) is highly addictive and may be harmful to your health. I mean that you must be very careful not to adopt bad habits and play a move on first sight without double check it. If you double check on CTS then you lose rating points.
Can CTS be recommended as training device? In my first enthusiasm I thought yes, but after some posts and comments of the Knights I am not so sure any more. There is a saying that you do not improve in chess when you play blitz, and CTS is surely blitz. I checked the top ten most active CTS users and found what I had suspected: With thousands of problems done their rating remained in a band of roughly 100 points. That is, a top rated player was top rated already when he started on CTS. And a player who was 1400 at the start is still there after thousands of problems.
So I come to the conclusion: CTS is an excellent device if you want to test your instant pattern recognition and basic tactic abilities. But forget it as a training tool.
I agree with Temposchlucker that the first step should be finding a target, and the second step finding a way to attack it or to prevent an attack on it. So what I need besides my X-Ray Training is a Target Scan Training Method. I hope to find one soon. I'll keep you informed.