Hi,
Currently there is no official guide / approaches to Migration from Crm 4.0 to Crm 5.0.
Anyway u can join the live meeting "Upgrading from CRM4 to CRM 2011". Follow the below link which is on 30 NOv 10:30 PM to 11:30 PM IST.
https://www.livemeeting.com/cc/usergroups/join?id=37B94J&role=attend&pw=5ths%2B6%5EBt
Hope it helps.
Thanks, Ranjitsingh R | http://mscrm-developer.blogspot.com/ | MS CRM Consultant