I think you are asking for everyone's "special recipe" (KFC reference)
I have doubts you will find direct answers to your question here.Everyone needs to do their own research, find their own methods and niches to build your keyword list with.
I would recommend:
1. NameBio's recent sale list
2. Pay attention to market trends
3. Keep up with Technology news/other news
4. Spent time reflecting on what is successful and what is not for you and learn to focus your efforts.
5. Define and refine your "special recipe" - and don't tell anyone.
If I'm looking in a particular niche, then I use searches and search trend records for ideas. I'll also look at the history of deleted names that were picked up, and see where interest is.
Most of the time though, I just look through lists of names, and if I see one I like, then I go off to grab it. Then I do a bit of swearing when I find that someone has beaten me to it.
Look around you at advertising boards, signs and the sides of trucks. Sometimes you can get inspiration from there. I remember a few actors did this for their stage names - Nosmo King and Max Headroom are two ancient ones that spring to mind. ( Both before my time before anybody comments )