Improvisation Tips, Hints, etc.

I'm doing a improvisation performance soon, its over Rock 'n' Roll by Zeppelin and i was wondering if tere was any tips on improvisation you had...

What's the key and mode which the song's in?

I have some lessons on the major scale and modes within - inside that I talk about improvising if you want to check that out.

Also, how good are you? (honest opinion) It depends on your playing ability to give off certain tips, because some of them require a lot of time, and I don't think you'll have enough if your performance is soon.

diddle around on scales until you find a cool phrase or think of one, then draw variations on it, let it evolve, etc. thats what paige, and virtually everyone else did.