Think of it this way. Say you have three hours to play. The first session, you may in fact take up that entire time playing at LEVEL ONE, warm-ups and group gelling. You may make it as far as LEVEL TWO, character and setting. It all depends on your ambitiousness. I myself would take my time, no matter how experienced the group, to explore the games and get to know the level of improv challenge we need.

In any case, a typical session will run:
-Start with LEVEL ONE warm-ups, every time, constantly upping the level of challenge from one session to the next
-Refresh on LEVEL TWO with reading from the setting (in this example, from the early chapters in Polaris), and playing See Me to revivify the characters in the story.
-Choose your new LEVEL THREE focus, looking at where you stopped last time, thinking about if you mastered that level (the rules should feel like second nature, before you choose to move on), and picking the next step.

Does that explain it?

Id like to try out some improv techniques as well with some friends soon. Do you use them instead of playing a session of Polaris? or do you use them before a session of Polaris as a warm up?