The key to self-care is believing you deserve to take care of yourself first and foremost.
Getting a massage
Eating wholesome, healthy food
Exercising
Doing yoga
Taking time to decompress
Taking time to pursue your passions and hobbies
Saying "no" to someone or something
Sitting in a coffee shop - people-watching, observing life
Taking a leisurely walk without a phone
Going on a bike ride
Painting
Writing in a journal
Going somewhere that's walking distance even if it's more expensive (i.e. a salon, a gym, etc)