Through sometimes bitter experience, you will find that you can't put anything in a policy until you get agreement from all the stakeholders. IT Security will want to have a say. HR should be involved. There may be multiple players in other departments.
At the end of the day, not only do you have to have policies, but you have to have clearly defined roles - who enforces the policy(not IT hopefully - HR should be the one telling someone's manager about policy violations), what the consequences are, the escalation etc.
I have seen good policies killed by indifferent line management or HR people who were not fully bought in to the idea.
You can probably get everyone in a room and do some brainstorming.
One good idea that has been effective is to make everyone sign the doc acknowledging the policy and have all new users sign the policy before granting them network access.
James