What is Twitter etiquette?

[...]

I'm new on twitter, and i am so used to facebook.
What is normal on twitter?
A random person followed me... is it considered mean to block him?
Or just tell me anything about twitter that i should know if i'm new to it... hahaha

[♥ Luke Walton]

Most people use Twitter for marketing or simply networking. Lock your page if you only want your friends to see your tweets.

[Bobby McFarside]

I'd tell you what twitter etiquette isn't if I didn't think a high ranking official of the AMA would hunt me down and kill me. But isn't it ironic that Weird Al already said what I couldn't?

[calaverre]

You can use Twitter for just about anything you want from keeping up with friends to business networking.

Etiquette-wise, you can tweet about whatever, but know that unless you lock your chirps, anyone on Twitter can read what your saying so don't say things which might get you into trouble or attract stalkers, etc. If you want to say something private to a friend, you can send a DM (direct message) and it'll be just for that person to see. If you're having an open convo with another Twitter user you can address that person with @username to get his attention.

Also, people think it's really annoying to repeatedly tweet the same thing (like pimping a website every five minutes). Fighting/arguments on Twitter are considered tacky too. Aside from that, it's a pretty open random forum.

As for someone following you, you don't have to follow that person back if you don't want to. If that user doesn't tweet about anything interesting to you, you don't have to clutter up your feed with his chirps.