We bought ours ahead of time from Gifts of a Lifetime for our May trip. I have a family of four and all of us wore them everyday at WDW. We each had a pin lanyard and just pinned it right on there.
We all loved the attention we received from the CM's. We were called by our names many, many times by the CM's and they always made a fuss over us, especially my kids. While we were waiting in line for a ride I overheard other people saying "look! They are guests of honor!"
It just makes you feel special. I can't imagine not having my GoH badge.