Any coaching tips for encouraging motivation and discipline??

Any coaching tips for encouraging motivation and discipline? I coach a college rugby club and half the members are totally dedicated, while the other half are slackers. I was wondering if any other coaches have faced this problem and if they had suggestions please. Thanks!

First,if motivation is what you're seeking for then make them realize what they are struggling for??Next,usually these slackers are just less motivated but you cant just let that be a total judgment of you upon them..Be a "total coach" up to a point they feel safe to share anything for you.Is it the same one services towards the one he care for than the one he doesn't keen of?? Discipline? Seek advice from martial arts "sensei"..they ought to know the essence of discipline well.