I've found that despite me having my phone on me almost all the time. Making sure the outside is never cracked and that the case is clean. I never pay much attention to the inside. This case meaning my apps and such. So here are some ways to clear out your phone:
1. Delete old pictures (meaning duplicates, blurries, exes)
2. Delete random notes
3. Put all your passwords on one note in your phone (hide the memo) and copy them down on paper.
4. Delete apps you don't use (basically, if you haven't played the game in over 2-3 weeks. Time to undownload. You've probably lost interest)
5. Organize apps with folders.
You can sort by color, letters, emojis, uses. Whatever works best
6. Saving things to a drive (like a google or one drive) saves room in your gallery for recent photos
7. Close unused chrome tabs
8. Delete old messages+call logs+emails
9. Log back into all your apps and do whatever you've been procrastinating on. (Example: setting up a profile or emailing someone back)
10. Change your phone background for a fresh start
11. Double check all your phone numbers are correct and delete contacts you don't need
