Here is a warm up exercise I use to practice scales/arpeggios/gypsy picking. I find it very useful.
There is a youtube video of the exercise here:
http://www.youtube.com/watch?v=l65eVHUxmDE&fmt=18
You can download a pdf of the exercise which has fingering and picking suggestions on the "Lessons" page of my website here:
http://www.timrobinsonguitar.com/
I hope you find it useful too.