Well...
Really you have two options, and the better one will not necessarily become apparent until you've tried your first 15-lapper!
Option 1:
No stops. Run a hard compound tyre (Racing Super Hard), and take a nice gentle pace, running right through to the finish. Try and keep reasonably close to the leader of the opposition (i.e. if you're leading, don't go scampering off into the distance, or if you're 2nd/3rd, keep in touch without hammering it to try and pass). Most likely your opposition will pit on lap 9/10, sometimes later, so as long as you're within 10sec at the halfway point, you should be fine.
Option 2:
One stop. Run Medium Soft or Soft, and run away from the field in the first five laps. Then hold the gap till 8/9/10 until your tyres have had it, then pit. You should still come out in the lead, but if not, and you've pitted late enough, you'll have nice fresh tyres to run through to the end.
My favoured option would be 1, but it's up to you really. It's always worth trying to conserve your tyres, and remember that if you've four yellows on the final lap, you can pull out a sprinter and often pull 1-2 seconds off the field when previously they've been maintaining the gap. This can make all the difference.
And finally... Don't get worked up if the AI cars go away from you in the first couple of laps if you're in a similar spec machine - it's likely that they'll pit earlier, gifting you the race.
Oh, and welcome to GTPlanet
