The club itself can't do a whole lot. If he wants to go, then he'll go.
However, the playing roster can make the club THE place to be (as if it isn't already) by instilling an even greater culture in the club and make it a club that players wouldn't want to leave.
How they do that I don't know as, apart from Will Hoppa, I can't remember the last time the club lost a player they really wanted to keep. The place must be unbelievable - just look at Ben Kennedy - played for the club for 2 years and the place got in his blood (until the Zorba thing anyway)............keep that culture going and he won't want to go anywhere.