Some sensible tips up above, plus:
Try a few off-road shoes. Personally I wear asics, but go for what feels right for YOU.
Stretch after. Start with easy pace to warm up. Wouldn’t recommend going hell for leather straight up hill – do a short loop prior to minimise risk of strains or tears.
Every other day to start.
Add another 2 or 3 routes if you can to give a bit of variety.
Don’t get hung up on times, HRMs etc. With respect, I doubt you’ll be troubling elite athletes so why fret about such things. Enjoy it for what it is.
Getting out the door on a filthy dark night can be an issue, but once out I’ve never regretted it.