Good advice here. Personally, I think the way my MSF started off was smart. They started you walking beside the bike (bike not started), then sitting on the bike and walking it (still not started), then starting it and learning to find the friction zone with the clutch lever.
Seems like a boring and slow way to get started, but it gives you a feel for the weight and size of the bike. And in reality, it only takes a bit of time. Just seems like forever when you're itching to ride for real
If you're headed out to a parking lot before the class and you've never ridden before, I think that's a smart way to start. Once you get acclimated to the clutch, start by riding around in big circles and just get comfortable with low speed starting / stopping / turning.
For me, once I learned how to deal with the stuff at slow speeds (stopping, starting, etc), everything above 1st gear was a piece of cake.
Edit: Didn't see that you already worked on the friction zone stuff. I'd give it a quick once over in the parking lot, then practice riding it up / down / around the parking lot at idle speeds and gradually build up a tiny bit of throttle each lap or pass.
Also, if you're riding a 250, let it warm up first. At least on mine, it isn't very well mannered at low speeds when it's cold.