Less obvious things to take care of before a trek.
Stretch before you start the trek. This will make your joints flexible in advance so that there are no surprises (sprains, muscle tears) during the trek.
If your trousers are hung low, they can interfere with your gluteal muscles (i.e. bum) as you walk. Similarly bulky things in your trouser pockets can mess with your thighs. Just make sure all muscles from hip downwards can contract and relax freely…
Except around your ankles. They could do with some support. Ankle height boots. Firmly laced.
Trim your toe nails. Especially the big toes. You really don’t want a toe nail coming off halfway through a trek.
Carry a plastic bag to hold your electronics for when it rains
Extra briefs (i.e. chaddi, undies), trousers, t-shirt
Carry medication for diarrhoea, nausea, tummy trouble.
A hacksaw blade is useful if you ever need to cut branches, rope, metal. It takes very little space. (This is only for emergencies, in usual circumstances: leave no trace.)
Make sure you are not carrying any precious/important non-essentials like ID cards, vehicle documents (except for ones related to the vehicle you are using for the trip), keys, jewellery.
Carry ORS or alternatives (Gatorade, enerzal) to avoid muscle cramps.
On foot care (from The Navy SEAL Physical Fitness Guide)