#1 Don't Micro-Manage - although this may be tempting, the key in helping people do their work is not to look over their shoulder, but rather empower them to do the job. Let them do their work in the manner that is in best keeping with their gifts, skills and abilities. Of course as a leader it is necessary to have periodic touch points to make sure everything is moving along, answer questions and encourage along the way - but let people be in control of their work processes.
#2 Communicate Clear Expectations - this dovetails into the first principle. If you give your team members clear expectations, with clear deadlines, with clearly defined outcomes, then they will be empowered and accountable to do what is being asked of them.
#3 Thank Often - it doesn't matter if your team members are volunteers or paid, people need to be appreciated. It doesn't have to be extravagant, just intentional.
#4 Give Performance Reviews - it is important for team members to count on periodic reviews of their performance (more often when first starting, then usually yearly from that point on).
#5 Ask Them Questions - since they are the closest to the job or task, the more and more they do their tasks, the more and more they are becoming the experts. Therefore ask them questions, seek their advice, let them have a greater voice into the work and the process they are engaged in.