To train tactics skills is really easy. It is necessary to solve tasks with different tactical ideas (distraction, decoying, x-ray) and then solve tasks that combine all the ideas. In due time I studied only one book on tactics (M.Blokh «The Art of Combination») and it was enough for me.
So, what does this process look like? You solve tasks which go from simple to the difficult. On simple tasks the foundation for tactical idea is based. Then «bang» and you turn out to solve more difficult challenges. Then switch to the next tactical idea.
Why are the results of tactics training on the Internet and computer programs worse?
1. You solve tasks without basic skills on tactic.
2. You acquire far less material.
3. Tasks on tactics aren't structured.
I recommend book M.Blokh "Combination Art" to all players who wants to improve their tactics skills.