As you add Twitter followers, chances are that they'll follow you back. It's tempting to just add everybody in the hopes of increasing your number of followers and inflating your own popularity.
But quality will serve you better than quantity when it comes to both your followers and those you decide to follow. Think about it: if you follow someone back who only followed you to inflate their own follower number, how likely is it that they'll actually pay attention to anything you say and engage with you or help you out with a retweet down the line?
Not very. On the flip side, if you add just anybody without regard to the quality of their tweets, then Twitter will become a giant time-suck as you wade through all of the noise to find anything of actual value.
How do you know? Before you follow someone, take a quick peek at their Twitter profile. If you don't see any @ replies (ie, they conversed with another Twitter user by adding @ in front of their username) or Tweet (ie, they re-post someone else's tweet), that's a good sign that that person isn ' t there to engage, and you can skip hitting that Follow button.
Of course there are exceptions – celebrities, some businesses, gurus in your field or other people you admire, find amusing or want to keep tabs on but are probably too busy to actively engage with their followers.
Another reason to be careful about who you follow is that you don't want to appear desperate. Try to keep the number of people you follow lower than your number of followers. A higher following to follower ratio makes you appear desperate for followers. Conversely, that's a good red flag to watch out for when deciding who you should follow. Regularly unfollowing “deadbeats,” or people who don't follow you back, is a good way to keep that ratio at a respectable level.