Motivation

I have found that motivating students differs greatly from student to student. It is important to talk with each student on a personal level to find out what is important to them. Once you know what is important to them then you can use that as your motivating tool.
For athletes, it is almost always sports related. They can't play if they don't keep up their grades. But know that they know, they only need a 75 average so you have to also talk to them about playing in college and what type of grades they will need to get in.
Once you have met your students parents, you can sometimes use them as a motivator. You will know just from talking to them who these parents are.
For some students, the candy and stickers will work. I also always do a contest around State Fair time (tickets), State Basketball Championships (tickets) and any concert that comes to town. I give away movie passes (if you know someone at a radio station then you can get these free) after every district test. These things appeal to any student.
Motivating students is not an easy thing to do. The important thing is to know your students. There is no fix all. Each case requires a different approach. Once you know your students then you can motivate each one personally.