Motivating staff for the best performance possible is a matter of finding the right drivers that interest them and reinforcing those drivers while providing negative reinforcement on other, unwanted behaviors. There are two main types of theories to motivate employees - the content theory (motivation is internal based on employee needs and wants) and process theory (external factors that can be used to influence employee behavior).
Two of the most famous content theories are Maslow's hierarchy (as shown above) and Herzberg's two factor theory. Maslow's theory proposes that lower order (physiological) needs must be satisfied before higher order (psychological) needs can be considered. Herzberg's theory falls in between Maslow's and other process theories and states that one set of factors causes motivation and satisfaction (content factors) and another set is responsible for dissatisfaction and low motivation (hygiene factors).
Process theories of motivation are primarily split up into Expectancy and Equity theories. Expectancy theory focuses on the relationship between effort, performance and rewards and as the name states, rests on expectations, instrumentality and valence. Equity theory is very much a match to the name - with equity theory, the employee is basically comparing themselves against others and depending upon that comparison choosing to be motivated or demotivated.
Behaviour modification (BMod) specifies the crucial role of the environment in shaping behaviour and states that behaviour is a function of its consequences. With BMod positive and negative reinforcement strengthen behaviour, and punishment and extinction weaken behaviour. Reinforcers can be either fixed or variable and the delivery can be either at a fixed interval or at some defined ratio. Partial reinforcement schedules have powerful effects on behaviour. By changing the ratio's of reinforcement, positive behaviors can be strengthened. This is known as behavioral shaping and is a very powerful tool.