As with any SharePoint migration, the jump from SharePoint on-premise to SharePoint Online will not be trivial. Quite a bit of planning will be involved in your migration project, but here are some tasks you can start doing right away to help make the process more enjoyable:
- Review customizations. This is likely the area that will require the most work. SharePoint Online doesn't support farm based solutions so any custom farm solutions you need to keep will have to be recreated as apps or sandboxed solutions.
- Be aware of capacities and capabilities of the platform. SharePoint Online supports files sized up to 250MB whereas SharePoint 2010/2013 on-premise will support files up to 2GB.
- Calculate bandwidth requirements. Your LAN is capable of handling quite a bit of throughput so probably won't be a bottleneck when it comes to performance of on-premise SharePoint. When moving to SharePoint Online, all of your data will be going over the Internet so you may need to increase the bandwidth of your current Internet connection and/or add additional connections.
- Clean up your content! Since you're planning to migrate your data to a new environment, take this opportunity to purge old, unnecessary data that you are not legally required to maintain. This will have multiple positive effects such as reduced migration time, lower storage costs, and better search results.
Thanks to Phil Cohen and Kimmo Forss who presented session #SPC152 (Migrating to SharePoint Online in Office 365 – Strategy and Best Practices) at this year's SharePoint Conference.
SharePoint Online Capacity Planning
SharePoint Online Planning Guide