Best things you can do are: (1) Avoid sick people, (2) wash your hands before touching food, and (3) take zinc lozenges if you feel a cold coming on.
They say to try not to instinctively touch your nose during the day as that is how it often transfers. I saw someone used hand sanitizer around his nostrils too a few times a day

I just remembered that melatonin has been explored as an early treatment as well a longer term treatment against 'long' Covid. Some hype the Methylene Blue as well, another strong antioxidant. I perhaps should have a home "med kit" for "emergencies" with high dose melatonin, high dose zinc and Methylene Blue to be taken at first sign of illness. I'm already taking a freakin' 100mg dose of melatonin nightly with Methylene Blue for a few days more since my pancreas is protesting ATM.
The hygienist recommended that I start supplementing with L-Lysine. I took her advices and honestly since then, I haven't had a canker sore.
I just remembered that, conversely, arginine might cause for example herpes flareups, and lysine was sort of the antidote. From memory. But arginine is supposedly good when recovering from surgeries along with zinc to improve wound healing and so on.