A few days back I was watching a video on martial arts where the instructor was insisting on practicing the basic moves. He was also stating that the same approach can be applied to other sports too. I also agree with him and believe that chess is not an exception here. I personally improved a lot at tactics by going back to basics.
The question is, what are those basic moves or the fundamental positions that chess players should practice? There are some books claiming that they have given the most important positions to learn but I think the choice of book varies from person to person. Here are my preferences:
For tactics, I am very much fond of Bain’s Chess tactics for Students. I myself finished it about 10 times and my students are also getting good results by repeating it. For the endgame I prefer the positions given in Chapter 3 of GM Ram by Rashid Ziyatdinov, though you need a coach to go through these positions. For checkmate training I prefer the first 306 positions from Chess: 5334 Problems, Combinations and Games by Laszlo Polgar.
Though, I strongly believe that one should give priority to their coach’s words above all because I myself gained around 200-300 points elo gain in 2 years coaching from Nigel.