TechNet has a great wiki article that discusses the considerations around syncing SQL Server to SQL Azure, as well as providing a walkthrough set of instructions on how to do it.
"SQL Azure Data Sync enables creating and scheduling regular synchronizations between SQL Server and SQL Azure databases. This article walks you through the process of creating custom synchronizations using the SQL Azure Data Sync web UI. This article should be used after you have read and understood the SQL Azure Data Sync How to Get Started and SQL Azure Data Sync Best Practices articles which get you up and running with SQL Azure Data Sync and help you plan and design an efficient synchronization system."
Read the embedded Wiki in its entirety: