Originally posted by ILS
Training specific abilities, meditating, acquiring greater knowledge, practising more advanced techniques, etc.
Having your limits tested, enduring trauma, etc. Which is why Jedi and Sith during war-times are typically the most powerful in a combat scenario.
Having a clear vision and focus for what you're trying to do, and being completely aligned with whatever aspect of the Force you're channelling. Basically having more control over your emotions opens the gateway for better Force usage. Being conflicted hampers you.
Also, on a more general level, you need something driving you. Something to make you angry, compassionate, determined, etc. If you don't have anything to increase your emotional stockpile you will stagnate.
Originally posted by Nephthys
Isn't there a quote that says that the only true way to increase mastery of the Force is through meditation and study, or something similar? That's likely how Ahsoka became so powerful.