Never click when the golfer is in the upswing or downswing... ha ha ha .. they will be very very pissed.
I guess as with most sports, use a tele lens, that is fairly fast (USM,SWM,HSM) etc.. high shutter, If you would like to get the whole golfer, then perhaps a medium aperture (f8 etc) should be good. push iso if need be to achieve the shutter speeds that will effectively freeze the golfer, and prevent hand shake etc. Monopods are a great help he he .
f/8? open up more. the longer the better. apparently some foreign courses only allow 300 or 400mm MINIMUM, to keep a safe working distance plus a distance that's far enough that the golfer can't hear the shooting...
what type of game are you shooting ? A friendly foursome ? A charity golf torunament ? A club level tournament ? An international torunament ?
Basic is you cannot be on the green for safety reason. You should not stand in front of the golfer - same reason unless you really want a shot of the golf ball hitting your front element. Use a long lens - at least 180mm which could be the bear minimum.
Bring sun block - your skin will thank u. Yr viewing lcd will almost certain not to be usable on the green - you need to know how to meter it right the first time.