When someone follows me on Twitter I want to follow them back. But I don't always do so. Here's a few reasons why.
1. You're an egg
When someone sets up a new Twitter account the default avatar is an egg. The egg isn't there for long on most (legitimate) accounts, so it's a pretty sure bet that when a follower's avatar is still eggified that account is a spam account. When I see the egg, I don't follow back. I like to know there's a real person behind the Twitter account. Having a non-egg avatar is a good first step in determining this.
2. Your bio is incomplete or full of a bunch of hashtag or shortened link nonsense
Again, I like to see that I'm following back a real person who is making an honest effort on Twitter. Your bio can be short, it can be long, but it should tell me something about yourself. A bio full of hashtags… why, why, why? You can't see me, but I'm shaking my head just thinking about it. Same goes for people who jam 4 different shortened links into their bio. Sorry, but I'm not going to click on something with a bunch of nonsense characters in it, especially when I don't know you.
3. Your Twitter stream is chock full of sell, sell, sell
A big part of Twitter is reciprocation. When I follow someone, it's because I've scanned their tweet stream and either been amused, entertained, or informed. If when I scan a tweet stream all I see are messages selling something—anything, really—you've just earned a no follow back from me. Indie writers are the worst about this. I sympathize with you all—I've got a couple of books to sell, too—but when my "All Friends" feed on TweetDeck is full of nothing but people selling, that starts to earn "no follow's".
4. You are a retweeting machine
Retweets are fine with me. But like many indulgences, moderation is important. When I see someone's stream is nothing but RT's, most of which are trying to sell something, I pass on following back.
5. You are a "social media expert"
Excuse me, but WTF is a 'social media expert'? That's a rhetorical question which I really don't want to know the answer to, by the way. Social media expert = go away, please.
6. You're having a multi-way conversation with your buds
I see this amongst the tech circles more so than elsewhere. Really, guys, get a (digital) room or pick up the phone. This doesn't usually garner an unfollow or 'no follow', but it comes close sometimes.
7. Don't try to sell me something or direct me to your blog, web site, or eBook via an auto-DM
When I follow someone back I'm fine with someone thanking me via an auto direct message. But not when it exists solely to tell me about something I don't want to buy. Following someone is about initiating a relationship. Exercise some tact and don't try to jam something down my throat before we've even had a chance to exchange pleasantries.
8. You've got a zillion followers but you're only following back a hundred people
This is rude. People find you interesting enough to follow. Give at least some of them some consideration and follow them back. The other way this happens is someone will follow, follow, follow. Then when those people start following them back the person unfollows, unfollows, unfollows. I guess it makes people feel important when they have a ton of followers and only follow a few back. Whatever, loser.
You'll notice I didn't call out any individuals above. I'm not pointing fingers, especially since I know I've been guilty of a few of those points myself. But I've moved on from, say, making my Twitter feed all about selling my eBooks. I get a lot of useful information from my followers and try to reciprocate as best I can. The key to success on getting a follow back from me (and most people, I think) is that old adage: just be yourself.