It all boils down to common sense anyway, doesn’t it? If you are quoting someone’s use of her 140 chars, then a verbatim “RT @source” makes a lot of sense. The Twitter I visit daily is full of interesting people who say important stuff in cool ways. There’s no point in rephrasing their tweets. If your Twitter doesn’t look like mine in this respect I suggest you use that unfollow button and start following interesting people instead. That’s what’s so good about your own timeline, it’s yours!

Passing on links could be a bit different though. Not always, because sometimes interesting people send their messages through both the link and the words they embed them in. (Apply common sense, remember?). But if you really are “just” passing on a link you should, really should:

1. Know what that link is about
2. Know what you think about the content

And then it shouldn’t be hard to craft your own words to follow the link. After all, you still want to reference who “sent” the link to you and the link occupies some space so you don’t have much space to fill anyway.

Maybe it’s this easy: If you care about that link being followed you’ll maximise the chances by letting your audience know why you recommend that link.

Or even simpler: Show respect!