I'm in school and we are just learning how to take blood and we were told as a rule that if a pt request a certain needle 9 times outa 10 its going to be a butterfly that you do what they ask....and if you stick and cant get it in the first 2 trys you go find someone else to stick them....use a different arm and watch the other person and see where they found the vein....and some places have this lil thingy that helps you find the vein...its like a lil ultravolet light thingy i forget the name of it..sorry...lobe manda O:)