1. Don't plan to drive anywhere on eclipse day (90% of the US lives within an 8hr drive of totality, so traffic will be horrible)
2. A 600-800mm lens is optimal for photography. Anything short of 200mm is useless.
3. Don't make any solid plans until 3-4 days before. Most places only have about 40% chance of it being clear.
4. If you're photographing the partial phases. Stop and check everything (batteries, memory card, focus, etc) about 5 min before totality.
5. If you have any technological issues during totality, just sit back and enjoy watching it.
6. On eclipse day, if you're in a place that has 2 min or more of totality, just stay there. There's not a lot to be gained by risking moving.
7. All across the US, the sun will be high in the sky, good horizons aren't necessary.