The Exchange team has been updating the Microsoft Exchange Server Deployment Assistant for the release of Exchange Server 2013 and the new Exchange Online, and it's ready to go! It's the best place for detailed instructions about deploying Exchange. A recent blog post on the Exchange Team blog, Now Available: Exchange Server 2013 Deployment Assistant, explains it really well.
The Exchange Deployment Assistant is a web-based tool that helps you deploy Exchange 2013 in your on-premises organization, configure a hybrid deployment between your on-premises organization and Office 365, or migrate to Office 365. It asks you a small set of simple questions and then, based on your answers, creates a customized checklist with instructions to deploy or configure Exchange 2013. Instead of trying to find what you need in the Exchange library, the Deployment Assistant gives you exactly the right information you need to complete your task.