Squat forward lean
When the weight gets close to maximal on the squat, I tend to lose form coming up out of the bottom, in that I lean forward excessively. This in turn necessitates something more like a good morning to get the bar up. It has been suggested to me that part of the problem may be that my glutes are not firing like they should. Naturally, I will go down in weight and work on form, but if the culprit indeed is too little involvement in the movement by the glutes, is there any point in supplementing by specific assistance exercises like RDL or some such? Is there some other focussed work that I can do to address the weakness in the most time efficient manor?
Look at it this way: if you lean way over in the squat and your back angle gets more horizontal, your knees have extended without moving the bar, right? This means that the posterior chain muscles -- the glutes and hamstrings -- now have to do all the work of lifting the bar without the help of the quads. They are obviously strong enough to do this, so it's not glute strength. It's failure to maintain the correct back angle -- failure to keep your "chest up" -- while the hips drive up out of the bottom. This is the result of more than just a glute problem; it's erector/lat/core/hamstring/glute/quad and brain. Same thing happens in a deadlift if you stick your butt up before the bar leaves the ground: muscles that should be doing their part don't because of a form problem, forcing other muscles to do the job in a way they aren't supposed to.
The fix is to lower the weight and keep your back angle constant as you drive hips up from the bottom. If you make your form perfect, whatever is weak in the chain will get more work and will thus catch up. I don't advocate the use of assistance exercises to fix the basic lifts, since this doesn't address the primary problem.