Select any text and tweet then right away. Twitter fast share also shows the number of word selectedTwitter fast share lets you share web pages to your Twitter feed with a click. You can select some text on any web page and hit the “Share on Twitter” button that appears besides the selected text.
As you are selecting text on a web page, this little tool will also display the exact character count of your tweet (see video) and thus you could save yourself from trimming characters later manually.