Allow for participation from all years. Your junior students will learn from the senior members. Cultivate future candidates by inviting them to leadership activities that you run for your present group. Ask staff members to get their students to think about why they are voting. Remind them that a good council can make a big difference in the number and quality of events that are run.
Negative campaigns get votes but hurt people and programs.
Please pass this information on to other advisors who would benefit.