When you arrive at the port, you get a boarding card with a number. The earlier you arrive, the lower your number, and the earlier you board. Boarding could start at about noon time, and the folks who arrived at 10:00 am would be the first to board. My guess is that you would not arrive at the port until 12:30 or so. So by the time you get to board, there will be many folks ahead of you.
When you board, go directly to the Palo reservation location (they will tell you this where this is when you check in). There may be a line, or everything may be gone. Put your name on the wait list, and check back later in the week.
You should also check often online prior to your departure. People's plans change, and an opening may become available.