Motivating students to push their limits
The most important aspect is the teacher's attitude. It sounds as though your students are already benefiting from yours.

As @Cinco says above,


  motivation is not a static, unchangeable property of particular students... A good teacher arouses the motivation indirectly, by creating the right environment for learning.  


Based on my experiences with some awesome professors, I will say DO


hold your students to high academic standards.
assume that the students are capable of doing more than they are currently doing.
show them how the subject you are teaching is relevant to them.
be enthusiastic.
recognize their great work, and always expect more and better in the future.


Perhaps most importantly, have fun! Enjoyment is contagious, and a good professor can make it fun to learn about anything. A great professor can make it fun to struggle and push against the limits of our abilities.

(Sorry, this is rather subjective...it is hard to quantify what makes a great teacher!)