Tempo runs where to start?

So I finished my 10K and was pretty proud of the results, but as I look at half marathon training plans most include a tempo run.  I have read and understand the basic concept but am unsure how to determine what my paces should be.

I can run a 10 minute mile pretty easy on the TM, and typically will increase speed at each x distance.  For a tempo would I go say from 6mph to 6.5 mph and then back to 6 for the cool down?  I know as I work harder it will become easier and these paces will be in constant flux but I am just trying to figure where to start.

Thanks.

the FIRST training plan that MacMadame posted a couple of days ago, which is pretty close to how i train for a marathon, has some good explanations of what tempo is vs. long etc.  of course for a half marathon you could probably up the pace on the shorter runs during training.  i copied the link here.

http://marathon.harvard.edu/images/first_first.pdf

A tempo run is not quite race pace but should be close and leave you feeling pretty tired. If you can do 10 minute pace for a long run then perhaps 8 and a half or 9 minutes for a tempo run would be about right.

FIRST also has a half-marathon plan. I'll see if I can scare up a link...

This should work:

http://www.runnersworld.com/article/0,7120,s6-238-244-258-9369-0,00.html