Don't do it!

Pasting from Word or another source where the original has formatting embedded will cause no end of headaches, as the formatting in what you copy/paste will conflict with the formatting you attempt to control yourself.  See Pasting from a Formatted Source for a foolproof approach. But if it is too late, this tutorial will help you clean it up.

You might also find this earlier tutorial on the same topic useful:

Entering Content with Copy and Paste