It starts with the book. I keep a list in my iPad of when galleys release so I know approximately when I should read them and in what order. Sometimes I'll break the reading order if there's one I really want to read and I don't have another to read imminently. So say it's time for me to read Killer Instinct. I walked over to the storage ottoman where I'm keeping my ARCs, plucked it out, and started reading. Or say it was time to start Chasing Power. I'd open my Kindle app and then open the e-galley. For any given galley, I always give myself the freedom to DNF it. There's no point in continuing to read a book I'm not enjoying at all. (Except in the case of The Jewel; I was a bit of a masochist when it came to that book.)
While reading an e-galley, I highlight and make a note about anything I want to include in the review. I also try to update my Goodreads status often while reading e-galleys or physical ARCs. When I started college, I realized it would take me much longer to read any given book. Therefore, I'd need to start taking notes when I read physical ARCs, too. So sometimes I use sticky notes and sometimes I'll take notes in my iPad.
After I've DNFed or finished the book, I might write the review right away. Doing it that way means I'll forget less. But I also like to wait at least a day, to give me time to mull over my thoughts. Since I schedule my reviews weeks in advance, I always have the opportunity to go back and edit something in, too. Then y'all will see it on the day it goes up.
And that's how I review a book! I hope this was an interesting post for y'all. I'd love to hear about your review processes, or if you have any questions, let's discuss in the comments!