Hubspot has published an interesting paper on social media marketing and are sharing one of the chapters on Twitter for free.
Here are the main takeaways (but do download the paper, it's a really interesting read)
1) Don't converse - rather share interesting content. Broadcasting beats conversation. Replying and being chatty doesn't serve your followers growth
2) It's very hard to overtweet - do as much as you can. The sweet spot is hit at 22 tweets a day but the curve goes down in a flat fashion after that.
3) Avoid talking about yourselves. Rather talk about what interesting stuff is happening outside. (exception: if you're a celebrity)
4) don't be negative (duh)
5) Make sure to have picture, bio & homepage. In your bio, don't be afraid to label yourself an expert. Tell others WHY they should follow you.
6) If you want retweets, ASK for them. Including the words "please retweet" has 4x the likelihood of getting a retweet than not including them
Not sure I agree with that, though - it makes you look like an attention-seeking douche.
7) Chance to get retweeted is highest on Fridays and any day between 3 and 5pm. Generally, prefer the afternoon for tweeting over the morning if you want to have a high CTR on links
8) Much higher likelihood to get retweets if you're original. People want to retweet NEW info. Also, much higher (4x) likelihood to get retweets if you include a link
9) Longer tweets get more clicks than short ones.
10) Highest click-through rate in tweets is when you place the link about 1/4 the way into the tweet - not at the end. E.g. "new blog post <LINK HERE> about a man, the sea and the futility of existence"
11) If you ’re sharing content you’ve found from other sources across the Web, tweet it as fast as you want. But when you ’re tweeting your own content to send traffic to your site, slow down and tweet it at a more deliberate pace.
12) Verbs and adverbs lead to more click-throughs than nouns & adjectives, especially action-oriented ones. "check this out". A less douchy version: "Tell me what you think"
And then one interesting comment I heard from marketer @hamishjcameron :
Even if the temptation is big, don't retweet friendly tweets. It's douchy. At a party, you wouldn't either walk around and say "hey, just want to tell you that Scott over there thinks I'm funny". Be on Twitter as you are in real life. Be a human.
