Always front and center. Then when the gun goes off, i start my watch and sprint forward. On occasion, I'll abruptly stop just past the timing mat if my watch has lost the GPS signal, tho. I've had people yell at me, but they're usually too far away to hear me explain my situation.
I always try for the first or second row in local road races. I am (read: was) a sub 15 5k runner, but my stature makes me look like a 17:30 runner - short, young-looking, too stocky for a runner, etc. There is always someone who doesn't know me and sizes me up before the race, just to step literally right in front of me. I've learned to let it go and just run. I used to just step back in front of them or mumble and find a different spot at the front. But the odds are, they are going to go out way too hard anyways. So second row is fine.
This type of stuff is the worst on the New England road circuit. Packs of guys (10+) running 5:45 pace for a 10 miler will crowd the front, while the guys running 4:50-5:15 pace are having to go around them after the first quarter mile. I've always failed to understand the psychology...
As a 74 yr young man who is married to a soccer mom with a 10 yr old, I resent that.