First, you may be putting the cart before the horse. You don't say in your post but it's important to consider where the motivation for such a policy is coming from. If this is something you've unilaterally and independently decided is a good idea, you're right...and you must immediately stop. Document retention is a policy that MUST have senior management buy-in, and you MUST get the highest levels of your organization to take on sponsorship of your effort if that's not already the case. If you don't, you'll go down in flames.
The previous poster is correct. Electronic and paper documents should be treated the same. Documents are documents are documents.
Many organizations are going to a one year retention policy. In the most extreme case all documents are deleted after one year, with the exception of those that are required by law to be retained longer (such as tax returns). Less extreme is a formal and enforced policy that all documents must be reviewed after one year and certified for retention. Those that aren't are deleted.
If you're in private industry you have a lot of choices, if you're in government you don't. NARA (National Archives and Records Administration) has a boatload of rules about how to handle documents. Their basic policy is nothing gets deleted ever, since everything is part of the historical record.
Generally speaking organizations have become acutely aware of what the lawyers call discoverability, which means if a document exists you can be required to produce it in the event your organization is the subject of a legal action. You can avoid the bullet if the subpoened document has been deleted.
You have a cultural issue to deal with as well, which is the natural human/professional desire to hold onto everything. Most people think there are two kinds of documents...useful, and potentially useful. We hate throwing away anything because, of course, the moment you shred something is the exact moment you'll actually need it. This is a mindset you can't ignore and will be your biggest problem implementing your policies.
Even if you're not in government you might want to check out the NARA guidelines. They've done a very thorough job researching and promulgating all kinds of policies with regard to document retention, deletion, and management.
