My evenings are currently dedicated to rereading the draft of my novel, Timeslip, and thinking about what changes to make. I sit in my armchair with a stack of lined Post-Its and a pen and go through chapter by chapter.
The text is already full of notes from when I was writing it the first time. I have a keyboard macro that adds a dated note (italics, with three asterisks in front so I can search them out), whenever I need a fact, or am worried about something, or remember that this affects something earlier in the narrative, but don't want to stop to find or fix. I now use those notes to figure out what I should do now. Often the note really says something like "oh, you can figure this out later". Well, "later" turns out to be...now.
The hardest thing is pushing the conflict. The book is a piece of commercial YA fiction (ostensibly), which is useful discipline for me. Clever notions, character development, odd facts--can't hide behind those. It's always painful to see how evasive I was when writing the first draft, how I stepped away from one character's need pushing against another's, how I let Doug, the main character, coast along, or evade confrontation, or get a break because the opponent is taking a break too. Well, Doug is going to pay now. Revision is the job of going out in a van and hunting down the escaped prisoners (aka "the characters") and putting them back to work on the narrative chain gang.
Otherwise, we have a failure to.... Well you know the drill.