1. Wear smart-glasses (normally round and small, wire rims)
2. During conversation, nod after key points (when the other person says something and gets excited) and say, "Exactly..." Make sure you trail off.
3. Same as #2, but if you want to deflate the person's ego, say, "I beg to differ." Instead of trailing off, walk away before they can ask any questions.
4. Quote from books. It really doesn't matter what. I have quoted from Calvin & Hobbes with a positive reaction. Garfield works as well.
More tips to come after I have the opportunity to test them out...