I've worked as the official photographer and now as a less official photographer. As an official photographer I didn't like when people didn't repect what I was doing, that's to say standing directly in front of me!! I take time to view and often ride the circuits before a shoot so I know the best, IMO, places to shoot from and the best way to move around the circuit. So not just a case of arriving whipping out the camera and racking off a couple of hundred shots. I also accepted that the circuit is an open public space and the public had a right to be wherever. The only spot I expected and would even demand was directly infront of the podium. Everywhere else was open, I knew that popular spaces would be heavily occupied so I always have a plan B. Generally I'm well known and people make space for me, 😆 , which is nice!
Not so sure about the insurance. As an official photographer I was covered by the Federation insurance and allowed into the circuits, as a less official photographer I would advise that you stay off the circuit.
Be careful of the riders… The genuine athletes and winners are all very nice, the Sunday riders out for a bit of fun are very nice, the "all the gear and no ideas" are a pain in the ar5e and will give you abuse for preventing them from winning if you get within 5m of the racing line and force them to take evasive action, losing valuable seconds…
If you're in a low position, watch out for the snotters!!! I think that's some form of cycling complement!!
Flash in a well lit area isn't generally a problem, be careful if it's a bit dark.
By all means tell the organiser what you're doing, I don't, again more often than not they already know me.
Private land I don't know as all races here are, I believe, on public space so not an issue.
And above all follow your common sense, not all that common, I know.
Enjoy.