Having a "checklist" that orients you from feet to head is very helpful. For example:
Are my feet, knees, hips, etc. all facing the correct way?
How is my weight centered? Am I over my feet? What's the distribution?
When I'm practicing footwork, am I hitting at the proper moment?
How am I using my lower body to help generate power? etc.
The advantange of solo practice is that you can go as slow as you want to practice body mechanics, allignment, proper form, etc.
Since a great deal of this will be lost when you're placed under stress, the more you "pack in" during solo practice the better. This is, after all, the whole point of "practice."
One other aspect of solo practice:
When practicing solo it's often helpful to imagine an opponent, or several opponents, on the receiving end of your techniques. This keeps you from mindlessly going through repetitions of movements without the proper mindset.
Stop when you start screaming obscenities at imaginary people, however.
Best,
Steve