Here are some experiments to do while practicing this:
- Keep the time by beating your foot on 1 and 3. This has been very helpful in my development.
- Carry one idea throughout an entire chorus (painful at times, but worth the focus).
- Try the tune in a different key.
- Work with contrasting tempos. Try a slow tune fast, or fast tune slow.
- Put in your harmonic substitutions, and see if you can carry more advanced harmonies all by yourself.
- Record your performance and see what your strong and weak points are.