Eating remotely well, exercising with some frequency, and exercising outdoors! I know lots of runners and gym rats who have gotten COVID b/c they train indoors. Those who run or train outdoors and either alone or in small groups have been less likely to get it, in part because there's no sharing of equipment, no public gym showers, etc, but also because Vitamin D and fresh air are extremely beneficial to health and wellness.
Beyond that, the only consistent advice to avoid COVID has always and only been to wash your hands frequently and social distance as much as and as often as possible.
Between good self-care, good hygiene, and maintaining reasonable distances, you greatly decrease your chances of catching COVID or pretty much anything else.