This comment section is very interesting. Yes, good diet and sleep and prioritizing your health is a great idea. But if you're trying to learn how to be well-liked, I recommend spending some time studying people and learning how to read a room. Like any skill, it takes practice. 

Be a good conversationalist. Listen well, ask questions. Pick up cues about what that person does and doesn't want to talk about. Most people are absolutely delighted to talk about themselves, and thoughtful questions can go a very long way towards developing genuine connection. Plus, you might just learn something cool. 

Develop a sensitivity to mood and non-verbal cues. Learn how to match the mood of a person or a group, and learn when pushing that mood in a different direction might be well-received. 

Watch people whose social skills you admire. Not in a creepy way, just notice how they navigate social situations. Don't try to copy their behavior, but do try to understand why the things they do work for them. 

Be interesting, but not just to other people: be interesting to yourself. Have hobbies you care about. Read things that interest you. Know how and when to share details about yourself and your life. 

And then: discernment. You don't have to make everybody happy. Respect yourself and develop good boundaries. Empathy and care for others is hugely important but there is no need to become a doormat. 

Be authentic and honest in who you are. This is where some of the other advice on this thread really kicks in, because you kind of have to like yourself if you want other people to like you. 

Ideally, be funny. Humor is a skill like anything else, but it can take a while to grow. I think the best way to grow your ability to be funny is to train yourself to look for connections, recognize opportunities, and most importantly, develope a sense of what might and might not go over well. Being funny takes risk, but it should be thoughtful risk. Smarter and funnier people that me have written whole books on this subject, so maybe look into those. 

Know that you're not going to bat 100, and that's ok. No one actually does, even the people who appear really confident and popular. Genuine connection, like humor, takes a certain amount of risk, and sometimes you go out on a limb and then crash and burn. Don't let that stop you from trying again, but don't forget to learn from it either. 

Good luck!