What is the 'best practice' for changing from 'Activities' to 'Fragments' for Android applications?

I am writing an application for Android platform. The application is already almost written for 2.x version, but I want to make it also for Honeycomb version. As you know, Honeycomb has 'Fragments' rather than 'Activities' for tab target.

There is about 30 activities in my application and it must be changed to fragments. It could be very hard word for me, so I want to know the 'best practice' about doing it.

Thanks.