Tickets can be bought online but we just dropped in and waiting 30 minutes for the next available tour slot; tickets are purchased based on date/time and are nontransferable to another date/time. In addition to local, child or senior discounts, they offer a student discount. I didn't have my college ID on me but they honored an email from my school account off my smartphone. Score for being a kid again.
The tour was less than an hour long. The "graveyard" lacks shade so bring water, sunglasses, wear sunscreen or whatever you need to keep yourself comfortable under the afternoon sun. The tour was spent mostly meandering through a path in the small lot surrounded by signage and listening to our guide talk about various sign's Vegas history, the hotel it was attached to and the trends that occurred in neon art. It was surprisingly very engaging.