I agree with getting used to walking uphill and down.
I used to run marathons, paved and on mild hill inclines were no big deal. Then I went to NYC and ran their course - I can’t recall how many bridges we crossed over but they were steep enough to make jelly out of unconditioned quadriceps, there’s a bit of clumsiness that comes when going back downhill.
Trekking seems so carefree and nonchalant, after a few miles your thighs down to your toes will feel all those irregularites that you have to compensate for trying to stabilize yourself on the terrain.
(Oh, don’t forget to pack a snow/ice scraper for the bears. 😊 )