Always run the inside curve. That's how they measure the course.

You can't really practice it. During the race you have to look ahead and always be planning your move.

If you're in the mid to back of the pack of a decent sized race, running the tangents is next to impossible since you'll have to cut people off constantly. It also seems to be these people that complain the most that a course is long according to their watch or phone. Since I am usually near the front or at the front, running the tangents is fairly easy. The last half marathon I ran was certified and my watch was only off by .03, but people were complaining that it was way too long. A lot of people have no clue if a course is certified or not, they just assume that their GPS device is the end all be all.

A few weeks ago, I just happened to compare the distances that my watches (Garmin 610 & 205) recorded on the certified courses I've run because I was curious about their accuracy. The distances ranged from 2 miles to a marathon. My Garmin 205 had 10 such races and my 610 has 6 races so far. Based on my results, the watches are very accurate. I was able to set up both watches to record my position every second which I assume would make them more accurate than those that only record your position every 2-5 seconds, or whatever the interval is. 9 of the 10 races with the 205 and 5 of the 6 races with the 610 were less than 1% off from the certified distance. The only two races outside of the 1%, but within 2%, were both 5k's. One of the 5k's was run in a downtown through a bunch of tall buildings which I'm sure had an affect on the signal strength at times. It was only .04 off, so if it was .01 closer it would've been within 1%.

The overall average accuracy of the 205 was 99.24% and 99.48% for the 610. Based on the results of my watches on certified courses, I feel comfortable saying that if my watch is within 1% of the distance of a race on a course that isn't certified, that the course is most likely the distance as advertised. Although, I only count PR's on certified courses.

you should always run the tangents

you should also understand that GPS isn't as accurate as we like to think it is - awesome article on course measure & GPS below

most courses will measure long on the GPS

http://hamptonhalf.com/hamptonhalf-GPS.html

^ This. Run the tangents, but your GPS is always going to read long on a certified course.

My last marathon my Garmin said 26.56. It seems like a cruel joke, but its just the way it is.

My Garmins have been short on 3 of 16 certified races. .01 short for a 5k, .03 for a 5 miler and .01 for a marathon. I'm not saying the courses were short, just the watch came up short.

Well, there is also the human element. A course can be measured perfectly, but if the RD doesn't set it up according to the layout that was measured, then the certification doesn't mean anything. Know what I'm sayin?