I'm a huge fan of anything that makes practice easier, more enjoyable and gives a huge return on a relatively low investment. This exercise is one that ticks all the boxes. If you want to improve on the following, then watch this short video:
- Memorising tricky passages
The idea is simple. You take a metronome and set it to say, 120BPM. At that tempo, 1/16th notes are quite fast so what you do is you keep the click running at the same tempo but you feel the 1/16ths at half the speed.
You're still practising whilst playing in time, but at this slower tempo you can really see, hear, and feel the issues going on. Once identified, you then want to iron them out. You can still build a solid foundation at the 'slower' tempo, then instantaneously switch to the real tempo.
It's funny how, if you stick with this over a period of time and are consistent, you can really notice improvements.
For more on practice check out these lessons.
It really doesn't matter what you play, it could be a hard piece like Teen Town, in which case you'd take a small passage from it and apply the same principles from the video. Or, it could just be some technical exercises.
I love focusing on more than one thing during practice so much that I wrote a whole book of technical exercises that draw on various important topics.
You may want to check out this lesson after you master this one.