Tetris the Grand Master 4 (that has been released recently on Steam) has a training mode that suggest to you where to place you pieces. You can even select diff

Tetris the Grand Master 4 (that has been released recently on Steam) has a training mode that suggest to you where to place you pieces. You can even select different goal for the CPU (survival, make as much Tetris as possible, make as much T-spin as possible, ...). Of course when it gets fast your brain cannot process the suggest and it's kinda useless, but it's a good first step. Also the fundamentals of Tetris are simple to recite: maximize your piece placement possibilities / minimize your piece dependencies, avoid overstacking over holes, be mindful of your piece mobility; this can boils down to "play flat but not too much".