"Find out what motivates your Team Member and play to that."
In the last 100 years, several motivation theories have developed around what motivates a person. Most notable are Maslow, McGregor, Ouchi, McLelland, Vroom, and Hertzerg. Suffice it to say each Team Member is motivated to contribute to your project for reasons you might not even know. Once we get beyond job security, salary, and benefits (called extrinsic, hygene factors), what else motivates your Team Member?
Positive, intrinsic motivating factors include: recognition, more responsibility, new challenges, the opportunity to grow, and self-actualization. These motivating factors  relate to how a person feels about themselves. While harder to discover, they are the most meaningful, and most effective motivators. They also might be the least costly to provide.
Still there is room for other motivators like time off, gift cards, and so on. The important point to note is that any reward given must be valued by the Team Member to be an effective motivator.
Consider giving rewards in public. This gesture can elevate the Team Member's self-esteem, which in itself is a positive motivator. In addition, a reward given in front of the team can also motivate other team members to perform. It is good strategy to reward the Team Members throughout the life cycle of the project, rather than wait until the project is completed.
So find out what motivates your Team Member. Work that into your conversations. Remind him/ her about the possible rewards. Then make good on your promises!   It will be worth it.