Greg Dodd shares a couple tips on creating SPNs for SQL Server Reporting Services:
Reporting Services often requires an SPN assigned to the account running the Reporting Services Service. You’ll know that you need to set this up when you try connecting to your Reporting Services instance from within the same domain and you are prompted for credentials. If SPN’s are setup correctly then your browser will work out the authentication for you and your users won’t need to login again.
Read on for an example, but also a pitfall and how to avoid it.