Microsoft will formally introduce Office 365 Tuesday at an event in New York City. The service is a rebranded, upgraded version of the company's Business Productivity Online Standard suite that also adds Office Web Apps to the mix.

For businesses that already use BPOS, the changes--especially if they go with one of the more basic editions of Office 365--won't be extreme. But a number of steps must be taken to ensure the transition is smooth. The good news: Microsoft is giving BPOS users a full year to move to Office 365, and it will also handle all data migration tasks.

Still, there are some must-dos.

The most basic step is to decide which version of Office 365 is right for your organization. Microsoft won't break out all the details until the launch event, but rest assured Office 365 plans and pricing won't fully escape Redmond's infamous complexity when it comes to licensing terms. The offerings range from a basic, small business edition that provides Outlook e-mail and little else for $2 per user, per month, to an enterprise-class service that includes standard Office 365 elements like Lync, SharePoint, and Office Web Apps, as well as the full desktop version of Office, for $27 per user, per month.

A mid-level offering includes most of the main BPOS features, plus Office Web, for $6 per user, per month. There likely will be myriad other options.

Deciding which version to go for is a research project in itself, but it will be necessary to fully vet the available packages to make sure you opt for the suite that's most appropriate for your organization's size and needs.

Second, check out the competition. BPOS-to-Office 365 shouldn't be too traumatic a switch, and Microsoft is providing plenty of tools and free advice on how to get it done. Still, it is a transition that will involve some work, so enterprises may as well take the opportunity to see what else is out there. That inevitably leads to Google. Google Apps doesn't offer the range of choices available with Office 365. Packages go from $5 per month per user for basic Gmail and Google Docs, to more expensive combinations that include business-class services like Postini archiving. There's no desktop version of Google Apps, it's all cloud. Some organizations, especially small and midsize businesses, may welcome that simplicity. The point is that a technology transition is a good time to explore alternatives.

If the decision is made to move to Office 365, it's essential to make sure users are running PCs and mobile devices that are compatible with the suite.

The system requirements from BPOS have changed significantly. For the most part, you'll need to ensure your company's computers are running the latest, or at least very recent, versions of Microsoft's (or for Mac users, Apple's) key client, server, and Web products.

The oldest version of Windows that will support Office 365 is Windows XP, Service Pack 3. Mac users will need at least OS X 10.5 or later. For Web access, users will need Internet Explorer 7 or later. On Macs, Safari 3 or later will do. Also note that Office 365 does not support Outlook 2003 or earlier versions. Know going in that the BPOS-to-Office 365 transition could require a host of upgrades throughout your infrastructure. Microsoft has published a full list of system requirements here.