I now realize that I will never be able to beat the semi-professional eclipse photographers. I have to take time to view it with my eyes instead of my camera. Now I've got some other questions. That's all for now, and I would like to thank you guys for your help. Still, in the 2 minutes before totality have a look to the west, the sky will appear darker there than in the east.
Diamond ring lasts one or two seconds., depending on location.
I suggest 100 asa or even 50 if you have only 300mm lens so you can enlarge and crop without showing too much grain. Just make sure you do not have to switch films or objectives during eclipse, there is no time for this. Depends what you prefer, negative or slide film. A 100 ISO to 200 ISO film would be a good choice. I agree that you must foresee the maximum time to actually look at the eclipse and enjoy it as much as you can.