I tweet quite frequently, so I've had to have my phone on silent ever since I got Twitter on it due to the amount it vibrates. I'd just prefer it if it only vibrated when I got DMd instead, as that is much less frequent, so how do I set this? I'm on a Samsung. Android, obviously.
The settings are found within the Twitter.com interface itself. Login to Twitter, click on the 'gear' icon on the upper right hand corner of the page and select 'settings' from the drop-down list. On the left panel that comes up, select 'Mobile', and that will give you a large check-box list underneath a heading 'My Phone'. You can then under 'Text Notifications' check 'Direct Messages' and de-select all the others (or choose the ones you want). You can also eliminate notifications during certain hours (such as when you are supposed to be sleeping for example). Lastly, I'm not sure about an Android phone, but you should be able to add the Twitter 'phone' as a contact, and set your phone to vibrate when you get a text from that 'number', and you should be all set.