Make sure you have a mid-roll and at the very least a post-roll.
Also it is even better if the mid-roll / post-roll is linked to the site the clip is from.
This extra effort is worth it.
To see a mid-roll / post-roll in action check here:
http://www.porn.com/dvds-player.html?scene=45649&
P.S.
www.pimproll.com has tons of hosted 2-3 mins flv clips with an easy exporter tool.
Tip #1 can be found here:
http://www.gofuckyourself.com/showthread.php?t=882420