Learning a method for calculating variations and practicing and applying the method on a regular basis improves your tactics. I can recommend the method described in the book (http://www.amazon.com/Secrets-Creative-Thinking-Champions-Progress/dp/3283005192). By doing exercises with pen and paper and 15 minutes per position, using this method, you will build up your calculation skills. There are no shortcuts.

Tactics, calculation, dynamic play. Topics often talked about but seldomly understood at their very depth. I cannot claim to cover the whole subject in this post. Yet hopefully I will scratch the surface of this vast subject. To become stronger in dynamic play, you need to understand the ingredients of dynamic play. There are at least two parts, calculation and vision. Calculation is the ability to enter different variations in your head and find the best moves for yourself and the opponent until you reach a position that you think you can evaluate. Vision is the ability to find ideas which in turn show you what moves or series of moves that are important to check.

Dynamic play is improved by training the calculation and vision skills. It is recommended to follow a calculation technique (as described in some books, e.g. Kotov) when calculating variations. By learning and applying the technique on a regular basis, your calculation will improve accordingly. Training your vision is more complex. You may have heard of patterns and that our brains memorize patterns when playing through grandmaster games and then we are able to apply these patterns in our own games. This most probably holds true. You should also collect ideas by reading annotated games and paying attention to the ideas that were described in these games. The ideas will also become patterns that you can apply in your own games.

Training correctly and truthfully is very hard. Training will give results. The best way to improve your dynamic play (I don't really like the term tactics because it somehow makes it sound more simple) is to train hard. To follow the training system that your books actually recommend. To get a personal trainer and/or mentor. To take every game seriously. To work hard at the board in each game. To analyze your games afterwards. To be self critical after every loss, draw and win. Dynamic play is a big part of every game. You have the static part and the dynamic part. So the dynamic play is at least half of every game. That being said, even 15 minutes a day will give great results, as long as you train properly. Happy hunting!