Here is a collection of methods what oneself can do to improve the own practice.

1. Being aware can help. The intention to observe the breath might already improve the breath. Once I said to my bf: And where is your breath? A sec later I saw how his belly moved. Alone thinking of the breath caused a deeper breath.
2. Taking pictures of oneself is very recommended. One can go a step further and compare the own pictures with those of more advanced yogis/yoginis.
3. Tiny movies even reveal more. I was not aware how often I play with my hair during a practice before I saw it in a movie.
4. It might be good to focus the attention on single body parts. A first question could be: Do I know how the feet position is? Second question could be: And how is my feet position. (Examples: Are the feet really hip width apart in down dog?) That way one can scan the body: knees, hands, hips, legs, chest, head. It’s recommended to focus on few things during a practice. After a practice one can ask oneself if one has checked what one wanted to check. Often it falls into oblivion. This has something to do with routine and the ability to concentrate.
5. The focus can also be the bandhas, the thougths that accompany a practice.

Feed-back from the outside from an advanced teacher is necessary. For sure.
Having a critical mind can also help to improve the own practice.

Knowing how an asana/vinyasa has to be does not mean that one is able to do it correctly.

I eat well and I’ve enough sleep for the time being and therefore I had a very good practice yesterday. Sometimes I eat well and I sleep enough and I’ve a lousy practice. Good practices are a gift from heaven. It seems so sometimes.

My focus today shall be the correct vinyasa count. I realized that I dawdle before I do a pose. There is no break or an extra breath between jumping through and doing the pose. One jumps directly into the pose.

How I remember the names of the asana: When I stand in samasthitih I always remember the name of the asana. When I’ve forgotten the name, I look it up later at home.