I would love to help you, (and glad you like the new subforum, I have no idea who pushed for it to be added
) but I wish you would narrow it down a bit.
If you understand all the attire conventions, as well as what's expected for manners and movement, you've got a big head start.
Your Sandie is a cute enough mover to pin in the hack, remember to use the whole ring, do not ride in a dressage frame but let her move out on a very light contact. Smile and act as if you're enjoying your lovely horse.
For over fences, striding counts! A lot! Make sure you have a good grasp of the 12 foot stride and what pace Sandie needs to get down the lines in the correct striding. My impression from your posts and photos is that Sandie likes to gallop a little and jump long and flat, make sure she goes to the base of her fences and jumps up and round.
Leads also count. If Sandie is ring smart enough to land correctly that's a huge bonus. If not, ride into the corner, rebalance and execute a neat, tidy change.
Remember, hunters means relaxed, steady pace, 8 perfect spots, 2 changes, and lookin' good doing it!