We really can't motivate anyone to do anything. What we can do is create an atmosphere in which people can feel motivated. Different people are motivated by different things; some by money, some by challenge, and some are self-motivated, etc. A goal is one of the best motivators there is. Differentiating levels of goals is a good way to create an atmosphere of motivation.
Recognition is one of the most powerful motivational tools you have to use. All people like and need to be recognized. Never mix good recognition with bad recognition, it doesn't work. Be sure you are being genuine, because the person being recognized knows whether it's accurate or not. Recognition is as simple as just making eye contact with someone in the grocery store and saying “Hi”.