Before beginning (or instead of) meditation
As you all know, the Buddha became enlightened by meditating for a very short period of time. And there are people who meditate their whole life and get not very far. For example, the zen monks. Why is that ?
I think that before one begins to meditate, one must cultivate awareness of all one's faults and impurities and irregularities in behaviour, thought and feeling. And then, through self-reeducation, one must go beyond it.
When it comes to excellent meditation, some of the Hindu demons of the past when they lived on the earth, used to meditate on Brahma for hundreds of years with unparalleled concentration. And after a great deal of meditation, Brahma used to appear before them and give them boons.
So, even demons can be excellent meditators.
Progress in meditation is a good thing, but unless the various bodies surrounding the divine spark, get purified, there is no chance of becoming enlightened. And, if through fault correction (gross and subtle), the various bodies are purified then there is no need whatsoever to meditate.