Make sure you are up-to-date on routine vaccines before every trip. These vaccines include measles-mumps-rubella (MMR), diphtheria-tetanus-pertussis, varicella (chickenpox), polio vaccine, and your yearly flu shot, do not forget pneumonia if you are older. When you get these shots, be sure to have them recorded on the Yellow Card provided by the World Health Organization; see International Certificate of Vaccination or Prophylaxis. The card for Yellow Fever, but you never know when you might travel to a country where that disease is present and you might need to get the shot before you go.
The US Center for Disease Control has vaccine recommendations, so take a look and decide if you want them.
Always wash your hands, wash your veggies, and all fruit before eating or cooking. Some people rinse the veggies in a chlorine sterilant that can be bought in the vegetable department of the Supermercado.
Like in the USA, do not drink water from rivers, streams, and lakes, but the city and town tap water is OK. If you must drink from wilderness sources, be sure to bring the water to a boil to sterilize it or use water filters or sterilant drops to purify it.
Update on January 22, 2021. I will be getting my first Covid vaccination shot next week and the second a month later. I intend to ask for and keep a paper record. When I next travel internationally, proof may be required to enter a foreign country or even return to the USA.