Hi, welcome!

1. Get familiar and involved in the discussion here and in the MeeGo Handset forum: http://forum.meego.com/forumdisplay.php?f=7

2. Download and install in your N900 MeeGo 1.1 unstable with the Handset UX when it is released.

3. Test and file bugs, specially about the underlying functionality (if MeeGo-Harmattan is your main target, otherwise feedback about the reference apps is welcome too).

4. Get the MeeGo updates, feel the progress, put your stress in the annoying platform bugs still open.

5. Wait for official MeeGo-Harmattan announcements and releases. Not much can be done about the MeeGo-Harmattan apps before their code/binaries are out.

These are steps that any N900 user with some time and patience can follow, hopefully while keeping their Maemo 5 stable intact in the device.

If you want to learn and improve as a developer a good entry point is to join a Maemo 5 community project you like and offer your help porting it to MeeGo or MeeGo-Harmattan. This might help you finding more bugs and rough edges in the underlying platforms, which is very good feedback for platform and application developers at this point.

Also important: enjoy the Summer!