2. Treat being social as a skill. Schedule time that you go out and force yourself to speak to people you don't know. Learn to care less about what others think of you, and learn to accept rejection.
3. Learn to be a "connector". Learn to talk to people. Listen to what they want and like. Connect them with others who like the same thing. Learn to cook and invite groups of people over for dinner and drinks/tea. Organize walks or hikes. Play poker, play board games, chess.
4. Keep track of everyone you speak to. Everyone. Write down what they mentioned they liked, who their family is, what matters to them. Maintain their contact. Reach out during holidays and birthdays in a heartfelt way.
5. (Edit) Oh yeah, practice EXCELLENT hygiene at all times. Shower in the morning after exercise and take care of your teeth, breath and body odor.