Stabilizer Jacks???

I've just about finished my frame and was thinking of stabilizer jacks. My question(s): 1. What are the preferred kind(scissor or standrd style) 2. Just on the back or on all 4 corners? 3. Or just not use them all together? 4. Etc, Etc Basically, any input would be helpful. Now is the time for me to decide about these so i can finish the frame up and get started on the rest! 
