Word to the wise.

Follow this Step by Step Migration guideline. It works well.

IMPORTANT: 

1. Upgrade Seblod BEFORE you upgrade Joomla
2. Upgrade ALL other add-ons to J3x 
3. Get rid of any add-ons you're not using AND any that do NOT upgradable to 3.x
4. Set your Joomla template as one of the common ones, Beez or ProtoStar, etc (then re-add your template back later) else you may get errors that confuse you, but really have nothing to do with how the upgrade went.
5. Along the way there is alot of cache purging and back ups to be made. MAKE THEM and take notes on where you are in the process.

I think that's it. Feel free to add to the list. For some reason, I have found upgrade information to be the most lacking on this forum. Maybe that's one of things a membership upgrade gets you.