On level terrain, adjust poles so that your forearms are parallel to the ground when you're standing still with your hands on the grips (neutral position). When going uphill, shorten poles so forearms are tilted slightly below neutral. When descending, extend them so arms are slightly above neutral. See a video demo at backpacker.com/trekpole.
Fix Problem Collapsing pole Solution Adjustable pole won't stay adjusted? A dirty or loose interior expander nut could be to blame. Fix it by unscrewing the bottom pole section beyond the "stop" mark to expose the nut. Wipe away dirt and manually tighten if it's loose.
Problem Lost/broken basket Solution In a pinch, replace it with the plastic lid from an insulated mug. Heat the tip of a knife over your stove, then cut an "x" in the center of the lid (just big enough to let the pole through). Position the lid on the pole, then wrap duct tape around the bottom of the pole to hold lid in place.