I rarely get sick but there is nothing I actively do to this, except for good hand hygiene and trying to breath through my mouth when I'm close to someone coughing or sneezing (the cold and flu viruses get to you through your nose, not your mouth, so I have read it helps if you breath through your mouth) and make sure there's a bit of everything in my diet. I get about one cold every 4 years. I don't remember last time I got sick with anything else.
Also, I don't smoke, I drink a glass of wine sometimes with my dinner, and never more than 2 when I go out, I don't like strong liquors. I don't like heavily processed junk food (I never eat McDonald's or KFC or anything such, not for health reasons, I honestly don't find that kind of food appealing).
I don't actively exercise, as in I don't go to the gym, or run, or do any kind of sport regularly. However I do walk a lot with my dog and I like hiking when i have the chance.
I eat whatever I want and I love chocolate and cakes. In my job I work nights regularly, and during night shifts I don't feel hungry so i usually just have a snack.
I eat everything, I don't follow any particular rules with food.
I am a healthy weight, my BMI is 22 or 23 last time I calculated it. I am 42. I don't remember when I last went to the GP! I think it may have been 2 years ago for a cervical smear.
Apart from that, I can't think of anything else, really.