So let's say you want more Twitter followers than the number you have now.
That makes sense! Wanting more Twitter followers is just a new-ish way of wanting more people to like you, and that's mostly what there is to life: hoping more people like you. (A warning: I'm not convinced this is a desire that can be met! You'll see people with 90,000 followers asking those 90,000 followers to help them get to 100,000 followers, and that's when, if you are paying attention, you'll realize you cannot win.)
So first you have to remember that not everyone likes you and some people never will and all you can really do about that is cry if you want to. And then you can consider trying these things, which might or might not help, but which have to be better ideas than telling you to hashtag everything or participate in #teamfollowback.
1. Have a voice.
There is something very cheesy about telling someone to be himself, but it must also be important and true or else it wouldn't come up so often. There's something that makes you YOU, and if you want Twitter followers who care about you/your life, you'll be that thing as much as possible. Sound like a human, is what I mean.
2. Follow people who might reasonably want to follow you back.
You should follow whomever you want, obviously, and you should never, ever, ever ask someone you just followed to follow you back, BUT! You ARE more likely to increase your follower count if some of the people you're following have some sort of connection to you that might make them interested in following you back.
3. Interact without being a pest.
Getting someone to notice you can be tough, especially since Twitter no longer sends out emails for each new follower. (My inbox feels so empty.) Do tweet at people you like, and favorite or RT their stuff when you really like it. Just don't be annoying. If you're responding to everything they say for attention, they're more likely to block than follow back. And no one likes it when you try to one-up a joke with a cleverer response.
4. Promote the people you like without expecting anything in return.
Because it's not just about getting them to follow you. People appreciate it when you spread their words and links because you genuinely think other people will enjoy them. Over time, you'll develop a reputation for being kind and generous, which will likely have an effect on your follower account. Acting entitled, however, or offering to retweet someone as part of an exchange just makes you look like a douche.
5. Know the difference between sharing your work and annoying self-promotion.
A good idea is linking your followers to a blog post you wrote. A bad idea is retweeting another person linking to your blog post and talking about how amazing you are. No one wants to follow someone who is endlessly trying to make a name for himself or herself. As in real life, you don't become popular by shouting, "HEY, LOOK HOW POPULAR I AM" at anyone who passes by.
6. Share links/news with a view attached.
If you're going to use your Twitter account to share links to things you've read, do so with a clearly expressed view attached. Anyone can link to a story and write "Interesting read" before the RT — taking "a side" makes it more likely that someone reading the same thing will really agree or really disagree with what you've written, and people like following people with whom they really agree (or really disagree!).
7. Be timely without being trite.
People respond well to tweets about breaking news, current events, and what happened on Catfish last night. But be aware: A huge amount of other people are also tweeting about these things. While it's good to keep your Twitter account relevant, make sure you're not just going for the obvious joke that 500 people made before you even woke up.
8. Live-tweet the events everyone watches.
Believe it or not, live-tweeting can easily get you followers. But there are some caveats! Again, you have to make sure what you're saying is interesting and unique — anyone can report on what they're seeing, but only the best live-tweeters make observations that are LOLworthy and retweetable. Also, you don't need to live-tweet everything. The major events (the Oscars, the Super Bowl) should suffice.
9. Care just enough, but don't obsess.
This is more about maintaining your sanity than it is about getting followers. Remember, it's just Twitter. At the same time, obsessing over your follower count can drag it down, especially if you let that show through your tweets. (Complaining about not having more followers is never a good look.) Also, when you obsess, you're more likely to tweet dumb things out of obligation. It's OK to just step away from the computer sometimes!
10. Be nice, dick.
This is the most important advice of all. And guess what — it doesn't just apply to Twitter! A lot of people seem to think that snark is the way to internet fame, and it really, really isn't. First of all, there is always going to be someone meaner and funnier than you out there. Second of all, no one likes an asshole. Oh, sure, they might keep you around for a while, but at the end of the day, kindness prevails. Your Twitter followers will be with you for the long haul, and they'll spread the love around.
In truth, there are probably only two ways to get a lot of Twitter followers: Be really good, or be really, famously bad.
And there's one more way, but it doesn't count, because the third way to get a lot of Twitter followers is to buy them. But if you buy them, you are not buying "followers" so much as you are "pieces of cold and empty internet space" with egg faces who have nothing to say and no capacity to read. And wouldn't that make you feel odd, when you really think about it? Buying all these fake eggs. Sometimes I just don't think we're thinking about it, any of it, at all. (Though now I'm imagining lying on a bed or maybe in a little inflatable pool with hundreds or thousands of hard-boiled eggs taken out of the refrigerator all around me, and in my head it seems nice. A new way to cool off in the summertime. But you would have to be careful when you got up, and maybe it would feel wrong to eat them later.)