Warm up: 20 minutes easy jog. Add in a couple pick ups to make the legs get fired up.
Main Set: 8x half a mile with 60-90 seconds rest. (the repeats are your "goal" half marathon pace. Not too fast to go to the well but not an easy jog along the beach. Example, your goal pace for a half marathon is 8 minute miles, so you do yours on 9 minutes or 9:30, that gets you roughly 60-90 seconds rest. And remember to hold as close to the same time for each repeat.
Cool down: 20 easy minutes of jogging.
Have a good run!