Too many weekend golfers ignore what seems to them to be a trivial part of the game, care of their clubs. As often as not they keep their clubs at home, and they find it quite easy not to clean them. But this costs strokes. If the grooves of an iron are not clean the club head will not put maximum backspin on the ball. During a round you should have a towel available so that the club face can be wiped clean after every shot. You should also clean the grooves by running a sharp object through them before every shot.
Caring for woods presents a different problem. Woods pick up moisture and are affected by sharp changes from very moist to very dry climates. To prevent any problems, you should soak your woods periodically in linseed oil. This seals the wood and keeps it from absorbing moisture. Some people oil the heads of their irons, presumably to keep them from rusting. I do not do this, and I don't recommend it, because anything that makes the face of the iron slick is likely to affect the flight of the ball.