If it "squeals", the belt is either too loose or glazed. Belt dressing or automatic transmission fluid is a temporary fix for a glazed belt.

If it's more of a "growl" than a squeal and feels "lumpy" or jerky, you're probably low on fluid. Low fluid will also be foamy. Top up the fluid and crank the steering lock to lock a few times with the front wheels off the ground to purge the air from the system. The fluid can leak through worn seals, in which case adding power steering leak-stop may get you another year out of it. You can also lose fluid if one of the connecting lines between the rack and spool valve is rusted through. These are just like steel brake lines.