Shinkansen from Osaka to Odawara

I'll be using JR pass to take Shinkansen from Shinagawa to Osaka and Osaka to Hakone. I need some advice as to how, where and when should I make the seat reservation?

Thank you

You can reserve a seat in advance in any JR station. It is free if you have a JR pass. I usually only reserve the evening before a trip but have often reserved only 40 to 30 minutes before departure.
Some people reserve a week in advance....
It all depends on the time of the year and day of the week. One should reserve early enough for travelling at holididay times.

You can also take a chance and line up for a non-reserved car. There are signs on the platforms that tell you the number for the cars with non-reserved seats an these numbers are also written on the edge of the platform.

Thank you for your reply.

We will be taking Shinkansen from Shinagawa to Osaka on 08 Dec and Osaka to Hakone (Odawara) on 11 Dec. Is it consider peak season whereby we need to reserve seats in advance?

It is not so much what day you travel as what time of day you travel. Having said that, because there are only two Hikari Shinkansens per hour, they can get quite full. I would say that the more there are in your group the earlier you should make your reservations.

I will be going to Hakone from Osaka (Shinsaibashi station) on 11 Dec. I intend to reserve seats in Tokyo.

Based on Hyperdia schedule, I can take the following :
8.23am Shinsaibishi(OsakaCity Midousuji Line)
8.36am - 8.50am ShinOsaka (SHINKANSEN KODAMA 642)
12.06pm Odawara

I have 2 questions :
1) why is there a time duration (8.36am - 8.50am)at ShinOsaka station? Is it time given to get to Shinkansen platform?

2) what happen if I missed the train which I have reserved? Can I take the next one?

Pls advise. Thank you.