Here’s a good article on service programs and binding directories, Article ID: 20172.
You may have to be a member to access it. But I think they have a limited subscription for free.
Keep it simple. Use the name of the service program and a two, three or four digit sequence number. Don’t try embedding too much information in the signature; just increment the number. The service program name is a simple identifier and a sequence number makes things easier to find. If you expect to have more than a thousand versions, then go with a four digit number. Or if you want something version/release, you can still go with four digits — two by two.
What more can you possibly need?
Note that nothing actually stops you from stepping outside of a simple standard if truly unusual needs dictate a more explicit signature. Just don’t try to do it as a normal act.