Merging Exchange Server

We currently have one domain and will be aquiring another that needs to be merged into our current infrastructure. These are currently two physically separate domains. When bringing them together, I need to move the exchange accounts from one domain to the other or link these two servers up some how. The main thing is to have complete integration when it comes to play. integration means being able to see public folders, all contact names and addresses in the global address book, scheduling, etc.

What is the best option to do this?