Modern Principles of Shaping - 5. If one door closes, find another!

I'm writing a 10 part blog post where I discuss the Modern Principles of Shaping by Karen Pryor, to help solidify them in my mind.

5. If one door closes, find another. If a particular shaping procedure is not progressing, try another way.

 

1. Depending on if this happens toward the end of within a shaping session, you may need to do this in real time.  I was trying this yesterday with Jazz with getting her to move her right paw so she can get toward a shake.  Very tough to separate actions, and easier if you can go the smoothest route.  
2. Alternatives for how to get the beginnings of a behavior: Capture, Targeting, Luring.  I tend to use capture, but it can slow down the process if the cat is just looking at me.  
3. Preparation for this part would be considering alternatives for how to get certain behaviors.  If you want the cat to raise its paw, maybe you move your hand in and the cat paws at it, or you lean forward, and the cat leans back and raises one paw in the process. 
4. This one is probably the hardest for me.  I tend to have a lot of patience, but I don't have as much as a cat.  

Outstanding Questions: How many times should you repeat something?  Should the same criteria be used for multiple rewards in a single session?  Or is switching between criteria every C/T OK?