alt Hacker NewsNo network is "smaller" than /64. All end-networks are /64.
Split subnets at four bit chunks.
Allocated networks, like to a home or small office, should be /56 or /60.
Then you have to think about link-local addresses and privacy addresses, and how to hand out IPv6 and configure DNS: SLAAC vs. DHCPv6 or some combination.
I have a rough draft of a beginner document but it's not ready. :)
(Pedantically) Maximum prefix length of /64 is only required if you want/need SLAAC. If you're assigning static addresses or using DHCPv6 for assignment you can go as small as you want. It's not weird to see /127 for tunnel subnets, for example.