Reinforcing effort and providing feedback

Ok elementary teachers I need some help.  I understand the importance of reinforcing the effort that students show but I need some new ideas.  What have you tried or implemented in order to reinforce your students?

Also how do you provide that feedback?  I teach kindergarten so it has to be something that is immediate or it doesn't mean anything to them.  They don't understand what they did to deserve it if the reward comes later.

Let me know your thoughts!  Thanks