Paste From an External Source in Microsoft Word
When pasting from another document or from the internet or some other source external to your document, you bring over the formatting of that text.
If you want the text to take on the formatting of your destination document (the one your pasting into), then use Edit Paste Special and choose Unformatted text.
Now, here's the really cool part. If you do this a lot, you can add this macro to your normal.dot file so you can paste the unformatted text with the click of a button:
The drawback? You won't bring any graphics with you, but you can copy those separately.