Classes are structured, with an agenda. I always felt that on my off days, I would work on my weaknesses, and things not covered during class.
Ditto here.
I try to have at least one evening in the week to practise basic kihon and tai sabaki. These are really the foundation of everything that I'll ever learn, so I try to repeat them as much as possible.
I also spend time almost every day on leg stretching. There is progress, but it is slow. It will take a lot of work to get to near split again.
Kicking is my weakest skill because it is not the focus of any of the martial arts I ever did. So for the last 2 months I started doing lots of exercises like exile. My technique still sucks, but at least it sucks less bad than 2 months ago.
Apart from those 2 things, I also regularly repeat all the forms / execises that are part of the grading curiculum. At present this is very little because a) I am new to ninpo, and b) many people in the dojo have no previous MA experience so we can't cover a lot in one session yet.
When I was doing jiu-jitsu, I would practise all curiculum forms several times per week. Starting at white belt and working my way up to my current grade.
I know it sounds cliche, but repetition is the key to learning. Even the white belt stuff is important. Class is for acquiring new material. Your own time is for learning and practising. Repeat everything hundreds or thousands of times, and you will notice a significant improvement in your techniques as time goes by.