The steering system on your car starts at the steering wheel at the driver's seat and goes down the steering column to the power steering assist, linkages, rods, knuckles, and wheels. There are many things that require regular maintenance and replacement in this system, any one of which could be a problem if not properly taken care of. Be sure to read your vehicles' owner's manual to find out what these intervals are and what needs to be done.
My car has "morning sickness"
If your car's steering is very sluggish in the morning, but is then fine after the car has been driven a little or when the day is warm, then it has what GM vehicle owner's often term "morning sickness." It's notable on General Motors front wheel cars, but can happen on many other makes as well.
The problem is in the spool valve housing on the power steering rack. It can become worn and cause hesitation and power steering fluid delivery issues. Check the valves for leaking and replace if necessary.
My car jerks to one side when I hit small bumps
At low speeds or when going over small bumps, your car shouldn't have any issues. If it pulls to one side or tries to turn into the bump, however, then you likely have an alignment issue. Have your alignment checked. You should have it checked every time you have any sort of collision, even if it otherwise seemed to cause no harm.
My car shimmies at high speeds
This is often caused by an out of balance wheel, bent wheel, or poor alignment. Have your wheels rotated and balanced to check for the first two problems. If that doesn't remedy it, get an alignment done. Note: never "fix" bent wheels, always replace them for safety's sake.
My steering is loose or not as responsive as it should be
This is nearly always due to worn tie rod ends, but can sometimes also be a worn idler arm or center link, depending on the vehicle model. Worn gears and a failing steering rack are also sometimes to blame.
Begin with the tie rod ends and work your way through the others.