Upgrading

At yesterday's meeting, we briefly discussed upgrading from Drupal 6 to 7. Let's use this thread to relate our experiences or best practices.

I've never seen a webinar from this consulting company, but it came across my inbox yesterday. It could be useful.
http://forumone.com/events/detail/healthy-drupal-7-upgrades

-dave

I have a multisite environment and are using the Omega theme as basetheme for every site. I'm now struggling with upgrading Omega 2.x to Omega 3.x. Upgrading breaks every websites subtheme. I get a WSOD?

How can i upgrade? What am i missing?

Sorry if this is a silly question - I've just started using Drupal last year and this is my first major upgrade.

I've got all my sites in one multi-site setup.

A couple of them are very simple, and basically good to go.

Can I upgrade just one of two of them at a time?

e.g. Could I create a new dir for drupal 7 and copy the sites over into it one at a time? (To eventually migrate all of them as the modules I need become available?)

FYI:

http://lx1.co.nz
http://nzmagic.co.nz

vs

http://amdramreview.co.nz
http://skeptember.com

Hi
I'd like to know what if I want to upgrade phpbb3.0.0 to phpbb3.0.1?
Will the module still work?
What is the best scenario to do the update?
Thanks