Why should I follow someone's account?
It is, in no way, obligatory to follow other accounts, on Twitter but it is not only useful but, almost, the point of having an account.
To follow an account, it is necessary to first access the account's profile, by clicking/pressing on the name, handle or avatar of the account. Then, the "Follow" button may be pressed. Once pressed, it will become an "Unfollow" button, so that a single further click/press reverses the decision.
Check, before following
However, before that, it may be sensible to check that the person behind the account is not the sort of person who will mess with your timeline and notifications by flooding you with information you may not want to see.
One clue is that, if they have a lot of numbers after their handle, it could indicate (but not prove that) they could be a bot or troll. Another clue may be that they joined recently, which can be seen on every profile. Again, this proves nothing but may be a clue.
A very good practice is to check out the accounts actual tweets. Are there few or none? Are they only retweeting and not posting original thoughts? Are their tweets in complete opposition to your own viewpoint? Do they tweet absusive or inciteful views? Have they been in pointless arguments with others of your own thinking?
All of the above are indications of the account being one, with which you would not want to be involved. If you decide that it is not one you do want to follow, DO NOT follow them or interact with them, in any way.You may even want to report them, if they break Twitter rules that you are familiar with.
Numbers of Followers
How many followers do you want? Linked to what has just been said, it’s a good idea to be clear on what sort of account you want to have.
Some people have very small accounts which they grow very organically and slowly, with no ambition to achieve huge numbers of followers. Good for them - nothing wrong with that. Big media stars have mega accounts with millions of followers, (and usually boring content). Many of us are somewhere in between.
Having a clear idea on how big you want to grow can be helpful.
Some general advice
If you want to keep your account small and contained, that’s fine. You don’t have to have a million followers. Many will tell you “Quality is more important than quantity” and looked at one way this is true. One of the reasons for using Twitter is to enjoy and learn from the contributions of people you are connected to. The more good ones you have, the more you can learn and enjoy. It is often found that, as a following grows, the content becomes more interesting. It is a good idea to strive to strike a balance, between quality and quantity, of followers.
Another tip is to be strict in following/following back only those accounts that generate content that interest/entertains/educates you. Connecting with people, who really do not share the same interests, is usually a false step. In the short term you get the warm feeling that you have more followers but this changes, when you actually read their content.
It may still be worth while, to take a calculated chance, now and, then. it’s good and gets you out of your box, to experience some very different content but, on the whole, if you can see you are not interested in what someone has to say, it is probably best to be honest with yourself, up front.
One other thing to bear in mind is that it seems to be easier to gain followers, as your account grows. The more followers you have, the more you get retweeted, the more people see your tweets and replies. This growth may, often, be exponential. Gaining early followers can be hard going but it gets much easier, as you go on.