If it looks messy, people will poster over top of you. A lot of students aren't going to check before they post you over. The University of Texas at Austin has developed an innovative postering technique that has helped prevent a lot of unsightly trash around campus. But a few years ago, we built some kiosks which are barrel-shaped, made out of redwood. Every six inches, we have these large elastic bands that are permanently attached.
Students can slip the posters under it.
They work great. Taping or stapling posters to walls eventually will peel off the paint, can damage drywall, and could end up costing your school and ultimately raise your tuition. Keep detailed notes about your observations of each location. Write down how many students walk by the boards and note how many actually stop for a minute or two to read posters. If you don't keep these records, when your leader graduates, transfers, or leaves school, then you'll have to start over from scratch.