I do most of my own covers so far. However, as I'm terrible at abstracts, and felt abstracts the only way to go for several science fiction novels, I made a deal with my nephew-in-law to do those.
For the ones I do, once I have a firm title for the book, I brainstorm as many different ideas as possible for the cover. Sometimes I come down to two I can't decide between, and make them both. If I still cannot decide between them, I email them to a few relatives and friends and ask their opinion. Sometimes this results in some tweaks to the winner, too.
As for the logistics of creation, those can be quite messy. That is, it all depends on what the cover's going to be. For instance, will it merely be a line drawing, or graphic pattern? Or have a lot of photographic elements? Will it need to be a wholly Photoshopped creation?
Sometimes I'll sketch something and scan it in, and play with it in Photoshop Elements. Sometimes I pull in photos of various sorts. Sometimes I use the vector program Inkscape for some items. I often use the Irfanview utility to help out, too.
Once the main cover image is done, I try out lots of different fonts for the cover text.
If you want more 'nuts and bolts' info on Kindle ebook cover creation, you can check out a guide I wrote: How to make your own Amazon Kindle ebook in just hours CHEAT SHEET
http://www.jmooneyham.com/cheat-sheet-how-to-make-your-own-amazon-kindle-ebook-in-hours.html