Alright, so this isn't exactly a tip or trick, it's more of a list :)
I recently got into using vaseline (petroleum jelly), and though most of these things aren't nail polish related specifically, this is a list of many of the things I've used vaseline for in the past:
1. It makes a fantastic cuticle balm.
2. Put it on before water marbling and it makes cleanup 100x easier.
3. If you have a cold, vaseline can rescue your poor chaffed nose.
4. Mix it with kool-aid or another powdered flavoring and make a great (and cheap) lip balm.
5. Slather vaseline on your hands/feet, put on cotton socks & leave overnight. Amazing softness!
6. It doesn't clog pores (as easily as it seems it would), so use it as a moisterizer for acne prone skin.
7. Helps easily take off tight rings.
8. Rub some vaseline on your polish bottle threads (the rings around the neck), and they won't ever get stuck!
9. Rub a tiny bit over your old polish, it ups the shine and makes it look new.
10. Use a tiny bit to shine up your favorite shoes/bags.
11. Use it when you put earrings in to make it easy and painless.
12. Mix it with sea salts and make a killer body scrub.
13. Helps get rid of razor burn.
14. A tiny bit on an old toothbrush will exfoliate your lips amazingly!
15. It can use as a makeshift makeup remover in a pinch :)
Have I said I love vaseline?