I’ve been using them all my life, wouldn’t hike without them!
Some things that haven’t been covered,
The way to measure for the minimum length is to play with a broomstick. Your elbow should be naturally bent, your forearm should be roughly parallel to the ground, and there should be no tension in your wrist. Measure the distance from top of your hand to the floor (usually you need centimeters :().
Too short a pole will straighten your arm and flex your wrist.
Try to get a pole(s) longer than you need, both for adjusting for hills and for “baskets” (you’ll lose a couple of inches before the basket hits the ground).
There’s 3 basic styles of handle,
straight (like a ski pole)
multi-grip (like a cane)
knob (like a ball at the end of the pole)
With an adjustable pole, the cane & ball style have a couple of big advantages.
You can change the way you hold the pole, long with your arm at a right angle to it like a ski pole or, short with your arm in line with it like a cane.
If your wearin’ a backpack you can put a split-ring (larger than the shaft, smaller than the handle) on the bottom of the shoulder strap and stow your pole like cops carry their nightsticks.
You can buy/make a pole bag for straight handles when you don’t need them.
Wrist straps are a must, they let you drop the pole(s) and use your hands, without losing them. Properly adjusted they also let you have a looser grip on the handle while keeping it in your hand.
The business end
Look for carbide tips, my Leki Lightwalk is 20+ years old, and the carbide looks the same as the day I bought it!
Rubber tip covers are also nice to have, better on rock and paved trails.
Baskets ain’t just for snow, there great in spring when the trails are muddy, and for crossing streams.
A couple of yards of cord, a rain poncho, and 1 or 2 poles make an emergency shelter that can be put up anywhere.