Graduate studies has developed many resources for your use as a Graduate Teaching assistant. You should visit their website and explore the materials available:
Graduate Studies: Graduate Teaching Assistant Handbook
(http://www.unl.edu/gtahandbook/handbook-intro) provides good tips for preparing for your class and teaching strategies.
Each Fall Semester Graduate Studies holds a campus-wide Workshop for Graduate Teaching Assistants (http://www.unl.edu/gtaworkshops/home). You should attend this workshop if possible.