I'm probably in the minority on this, but I'm not big on elaborate warm ups. On squat or dead maxes, I typically just do a triple with 225, a single with 315, a single with 405, ect. until I get to where I want to be.
My focus is not so much on actually warming up as it is making sure my form is there and making sure that mentally anything short of my max feels like a joke. This gives me the confidence I need. Many times on squats, I don't even attempt to do a full range squat until I get to some heavier attempts. Not sure I would recommend this; it's just my way. Like Clint, once I get within about 100-120 lbs of a max attempt, I go ahead and try the max rather than continuing to go up by 90 lb increments.