Just before anyone chimes in with some contradictory bullshit, there are some coaches/specialists who say that the only way your glutes don't "fire" is if you have some sort of "lesion" or injury and the problem is bad technique/motor pattern. They are right, but some people need the right warm up to be able to use the right motor pattern until it becomes natural.
I got this from Dr. Stuart McGill (in a book, not in person): warm up with lying side raises followed by glute bridges. What I was doing is two sets of 20 reps for the side raises, hand on the side of the hip (biofeedback) and focusing on using that side of the glute. Then glute bridges with external rotation (try to open your hips as you do it) with 5 sec. holds until I "feel the burn". I have since dropped the side raises but the way my deadlifts went today I should probably bring them back.
I was looking at Matt Wenning's facebook page a couple of months ago. He does training seminars with Ed Coan and Charles Poliquin. He said something about max deadlift performance increasing after static stretching of the hip flexors. I tried this out twice, once during a deload (hard to tell if it helped) and another time before I hit my deadlift PR - which had not leg shaking (as I mentioned in another thread) and looked like I had another 30lbs., which would have put me 40lbs. over my DL today. All I did before is a 20 sec. hip flexor stretch for each side before the first 3 dl warm ups. Try it and see if it makes a difference, I wish I had done it today.