Buy high fluorine toothpaste and put a TINY (I mean, miniscule amount) on your toothbrush. There should be only a few speckles of the stuff on there. Then brush just enough to ensure each and every nook and cranny is covered in the stuff, rinse and spit. If the next time you go to brush you still taste the toothpaste, you put on too much and therefore don't need to reapply it. Just put on a little less next time.

Never had a cavity since I started doing that, and I'm not even a 1/16th through the tube. Best money I ever spent.

::: spoiler EDIT: A few other dental tricks that will help dramatically:

1. You don't need to brush twice a day, once is plenty and preferably before bed
2. Don't brush right after eating/drinking especially if it was acidic, that tears your enamel apart
3. Use only a pea-sized blob of toothpaste, if you use it like they show you in the commercials, you're an idiot
4. The primary goal of brushing is to apply fluoride, the secondary goal is to get shit out of your gums
5. Tooth whitening is a scam designed to poke at your insecurities. If you buy into it, you're an idiot
6. Dr. Fortnite says floss every night. Use a water flosser or pay attention to how your dentist flosses as their technique is immaculate
7. All floss is blood-flavored, do not try to push back against this universal truth for it is absolute
8. There is no sensation more elating than your dentist actually being impressed at your dental health
9. Some toothpastes and flosses cause cancer, research which ones and stay away from them
10. A Colgate tee shirt looks almost exactly like a supreme one and costs a fraction of the price