It is a given that you need to make the most of the social media if you are in some form of activity that involves other people. We are not speaking of only businesses here. Even if you have a charitable organization, or if you are part of a voluntary club, or are associated with a meetup group, it is absolutely essential to you are visible on the social media world.
Facebook and Twitter are definitely the best bets if you want to bring your name out into the open. While Facebook helps you to put your posts up and share your activities with other people, Twitter is more about posting short statuses (known as tweets) with their links. Twitter is good for people who are searching about a particular thing because it uses hashtags. Though it does not have much content (it is classified as a microblogging site), Twitter does allow people to associate with each other and you can easily find something that you want to, and even know more about it through the tweets that others have made on the related topic.
There are other places where you need to be visible. One of these is LinkedIn, where you can make a professional profile of yourself, almost like an online resume, and keep yourself visible to people who might have a professional interest in you. Then there is Pinterest, and also Instagram, which is more about sharing pictures related to topics of your interest.
You can also consider YouTube, which allows you video marketing. Some activities would do very well with a video presentation, and you should definitely milk the potential of YouTube for whatever it is worth.
In addition, there might be special groups that cater to your interest, whether that is cooking, photography, movie direction, reading books, etc. Find out such groups and be a part of them, and see your network grow.