I will be shooting a marathon tomorrow with the D500 so anyone offer any tips on the best settings, like how many focus points to select and what metering mode works best, also what would be the best shutter speed?
Well first of all there is no "Best". Exact settings will depend on things like what sort of shot you want, what lens you're using and prevailing environment.
When it comes to metering I tend to try Matrix first and see how well it works. If there's something screwing with Matrix, like a lot of bright sky and it's pulling my exposure down, as happens so often when in Matrix, I'll drop down to a more restrictive mode like Center Weighted, and if that's not working I'll drop down to Spot. I tend to use the least restrictive mode that I can but Matrix seems all too easily confused, tends to over-expose with a lot of my lenses and I find myself using Exposure Compensation with it a lot which I find annoying. Still, when Matrix works, it works.
As for aperture, when shooting people I tend to hang out in the f/4 to f/8 zone generally speaking but again, it all depends on what you want out of the shot. Use the aperture that gives you just enough depth of field, but no more; the one that balances out the shutter speed and ISO you need to achieve the effect your after in your shot.
As for shutter speed, if you want crisp, motion-blur free shots I would be shooting around 1/500 or so. If you want something more dynamic, try panning runners at something like 1/125 or 1/60. When it comes to focus points the more erratic the motion the more focus points I use but runners you can pretty well predict so something like D9 would be fine in my opinion, especially if you're panning.
Lastly, burst mode will be your friend for this shoot.
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