When i first started doing halves i would check my time at every mile mark and work out the average, so that i could then estimate my finishing time. Over the years i have started to look less at my watch and plan the race in groups of miles.
For example if i was aiming at under 1hr 30 my plan would be to do the first 3 miles in 20 mins, repeating the process to get to mile 12 in 1 hr 20 leaving 10 mins for the last mile and a bit, giving me a margin of error of about 2 mins. I find that by thinking in groups of miles and having 4 targets in the race for 3, 6, 9, and 12 miles puts less pressure on each single mile and caters for the vagaries of the ups and downs better.
For other races i might set a target at 5 and 10 miles as i did at my last half. This depends on how long since my last half and appropriate fitness to be confident that i will run consistently.
So what do you do?
For example if i was aiming at under 1hr 30 my plan would be to do the first 3 miles in 20 mins, repeating the process to get to mile 12 in 1 hr 20 leaving 10 mins for the last mile and a bit, giving me a margin of error of about 2 mins. I find that by thinking in groups of miles and having 4 targets in the race for 3, 6, 9, and 12 miles puts less pressure on each single mile and caters for the vagaries of the ups and downs better.
For other races i might set a target at 5 and 10 miles as i did at my last half. This depends on how long since my last half and appropriate fitness to be confident that i will run consistently.
So what do you do?