I'm pretty sure the replies to this thread will be from people who are retaking it. Anyone who did well enough on it probably doesn't care about what they could've/should've done differently.
Here are the things I am doing and will continue to do differently.
1. Review all of the content.
2. Not going to skip over things I struggle with because "this probably won't be on the mcat anyway"
3. Doing practice passages, not just discretes.
4. Doing practice FLs
5. Making sure I understand a concept rather than just memorizing
6. Try to help others who are struggling with concepts I understand
7. Ask questions and accept that I do and will need help a lot