If you have status with a carrier that upgrades you for free and will allow you to upgrade companions at the airport, use it. I look for interesting (read - good looking) people to talk to at the gate, then I attempt to upgrade them into first class with me. You make a friend at the least, if your real lucky . . .
This tip is also great for military members you notice at the gate, they are protecting the country, upgrading them to first class is a great way to say thanks.

Also, if you watch movies on your PC (Netflix is great) on the flight, carry a headphone splitter so you can allow your seat mate to watch with you. It's much more fun to laugh at the movie together than alone.