I booked my Shinkansen ticket from Osaka to Tokyo four days before my travel date at Midori-no-madoguchi office using my JR Rail Pass. I wanted to leave early in the a.m. and knew if I left it too late, I would not get the departure I wanted.
Drop bags off at the hotel
Find an Information Centre to get acclimatized
Get some food and water and take a break and plan you next few hours