ARIN has given IPv6 addressing plan for service providers. The points of IPv6 allocation is given below:-

1. Separate address block for infrastructure from other uses (enterprise, loopbacks),it may be two /48s per PoP.
2. Each individual site should receive a /48 assignment which 65536 subnets (2^16).
3. Any prefixes shorter than /48 will only be assigned when there is written justification to show that this prefix will meet the RIR HD ratio guidelines within 5 years.
4. Each PoP is a site therefore assign a /48 for infrastructure.
5. No subnets will use prefixes longer than /64.
6. Assign a /64 per LAN / VLAN / subnet.
7. The enterprise network should receive a prefix sufficient to provide a /48 allocation for each site (office/campus/PoP) at which the company has employees or systems.
8. If you need private addresses, generate a ULA prefix as defined in RFC 4193.
Source:- ARIN WIki