Use “RT:” – the label “Retweeting:” and “Reading:” work as well.
If you'd like, you can credit the original poster by simply using the @reply, for example: “@originalPoster”.
Add the link you want to retweet along with a quick note about the link.
Here is an example of retweeting:
RT: @originalPoster The best Twitter Layouts http://freecodesource.com – great tips