I think that it has a narrow meaning and a broad meaning.

Narrow meaning starts with hygiene. Gum health is very important as gum disease can lead to cardiovascular disease, so the most important step is probably flossing. Dental tape is better than dental floss. When you floss, do not just go up and down, but also sideways. Water flossers are recommended to supplement string flossing. I got a Waterpik flosser but now have to figure out how to use it...

Further on dental hygiene, brushing with fluoride toothpaste and rinsing every other day with ACT fluoride mouthwash (for 60 seconds and then for 30 minutes no eating or drinking or water in the mouth) are also essential.

Moisturizing skin is key (any store bought moisturizing cream would do - CeraVe is a great brand that does not cost a lot of money).

Sunscreen on face, neck and hands when going outside; mineral sunscreen is better because you can put it right before sun exposure.

If not pregnant or nursing, prescription-strength Retin-A at bedtime.

If you have a chronic illness that requires taking pharmaceutical medications, then taking them (and putting them into a weekly pillbox so that you do not forget) is also part of self-care).

If you need supplements, such as vitamin D or Fish oil or Melatonin, then taking them is also self-care, but beware of scores of useless supplements out there.

Getting enough sleep on a regular schedule is self-care - probably one of the key factors.

Getting some sun during the day is self-care, and for people with seasonal affective disorder, using their light-box is self-care, too.

Getting regular physical exam, annual skin care exam, annual eye exam is all self-care, but you need access to healthcare for that.

Keeping yourself well hydrated is self-care, almost as important as sleep.

If you like coffee, then, based on mounting evidence of its beneficial properties, you can think of drinking coffee as self-care. Same for tea. Safe for fermented milk products that boost immunity and promote gut health. But if you do not like them, it is not worth forcing yourself to eat or drink them.

Eating a varied diet with enough protein, fat, complex carbs and fiber is self-care. Making sure that it is palatable and aesthetically pleasing is self-care too.

Keeping your residence tidy and clean is self-care for most people, but there are people who exist best among "artistic messes" and for them cleanliness is not self-care.

If you have a creative / artistic side that needs and outlet, then finding a venue to express your creativity is self-care for you.

If you have a nurturing personality, then finding an expression for that would be self-care for you - say, if you like baby animals, then volunteering at a shelter would be self-care for you, but if you indifferent towards animals, then such volunteering would feel forced for you and would not constitute self-care.

If something is bothering you and you need to see a doctor for it, then seeing the dr promptly is self-care for you, but again, for that you need access to healthcare.

Most people do better with some routines and regularity and if that applies to you, then instituting those regular patterns to what you do (daily, weekly, monthly, yearly) would be self-care for you, but if you are somebody for whom chaos and spontaneity are invigorating and inspiring, then you better stick with them.

If you are learning something new, then learning it according to your learning style (there are 7 styles) and not forcing yourself to adjust to another's mold would be practicing self-care for you.

If you like organized sports or organized exercise practice, then doing what you like would be self-care for you, but if you do not like them, then swimming solo or going for a walk and shooting pictures with your phone camera would be self-care for you and forcing yourself to take gym classes would not.

I personally find restorative yoga a necessary step of self-care and I go to a class weekly and plan to also practice at home.

Doing what you like is very important. Giving yourself permission not to do something just because an "authority" says that it is "good for you" is key.

All the best!