I just checked NH's web site. Tokuwari discounts are cheaper than Web-wari, aren't they? Esp. the early morning 609.

I have bought tokuwari several times. For them, all you need to do is to book ahead (normally one day before the departure date) so long as a seat is available. You can keep the seat and lock in the fare without paying for it (and without giving a credit number) until up to something like 20 minutes before the departure. You can just go to a check-in counter at HND and pay with a credit card.