I've been twittering now for a few months. I've also been avidly both writing and reading tweets. I've noticed a few things about subscriptions on the website, because people sub and unsub from me pretty much every day. 

1) Spammers get ditched pretty quickly.

I subscribed to a woman named Susan Powter. She wrote a book in the nineties about how to get thin and stay thin without having to do some crazy diet. It was an awesome book, and I took some valuable lessons from it (the basic gist of the book is this: choose what you eat for what's in it, not because it's easy or tasty). She twittered like she was trying to write another one, except that this time, it read like a food journal. No word of a lie, the woman tweeted everything she ate and every hour she spent in the gym. So I would get to my twitter page and have to scroll through every snack and meal that the woman'd had since the last time I checked the site. I unsubbed after about three days.

2) If you don't post at all, people will unsubscribe.

I subscribe to the friends I have on twitter. It's what we do. But some of them just never post, so they skew my stats (I don't like to follow too many more people than follow me, otherwise it looks needy) and I ditch them. No insult, but if you don't make it worth people's while, they'll unsubscribe.

3) People stalk the "follow" lists of people they follow.

For example, I decided to follow zephyf1 because I saw her on Nico Rosberg's follow list and she had tweeted about nanowrimo. I've since been followed by a couple of the minor F1 folk because she follows me. Stephen Fry follows Alan Davies and Bill Bailey. I decided to follow them 1) because they're cool, 2) because I knew that their accounts were legit (unlike the original Nelsinho Piquet that I followed. The real Nelson Angelo Piquet Jr has since got himself a twitter account).

4) People who don't speak English as a mother tongue will follow you.

Google translate rocks. People use google translate if they don't understand your posts. I use GT for all the Brazilian F1 drivers who have twitter accounts, because they all tweet in Portugese (my Portugese extends to "May I have a Savanna Dry" and "I don't want anything, you can go away now", and reading tweets is a little more complicated than that). So please, for the ease of use of your subscribers, do a couple of things: 1) spell correctly (google translate doesn't recognise misspelled words). This includes words like "cooooool" and "freeeeeezing", and 2) limit your use of slang or put a P.S. explaining your slang word. For example, if you're going to talk about chongololos, explain what a chongololo is (for my solitary Irish reader, a chongololo is a millipede that grows up to about 20cm long and is black with orange pinstripes). Also, if you're going to tweet in Afrikaans/isiXhosa/isiZulu, it's polite to provide an English translation either in the second half of your tweet or in a second tweet.

5) There is a line between too much and too little.

Some people (*cough* Rob Brydon *cough*) only tweet about their work. It's a bit boring, to be honest. On the other hand, I nearly unsubbed from Stephen Fry when he shared about the consistency of his bowel movements. The only thing that stopped me from leaving him in the dirt was his immense coolness. The balance is hard to find, but you'll find it.

Basically, the short version of this is tweet what you'd want to read from others. I'm sure that you're all awesome twitterers, but these things must be said. I don't claim to find the balance on these all the time, but they're things I've noticed. People unsub from me when I share too much or too often, so I haven't found the perfect balance yet. Alternatively, other people have lower tolerances for random information than me. Let's face it, twitter is all about voyeuristically stalking other people, so I suppose one does ask for a bit of overshare when one subscribes!