What have y'all found to be the best leg accessory lifts?
Personally, I don't do a whole ton, given that squats and deadlifts crush your legs if done properly. Usually, I do RDL's on Squat day, and Front Squats on Deadlift days. These, combined with sprints and a long run here or there, and some olympic lifts, are generally all I need.
When in doubt - do some more squats
More squatting (front squat, high bar squat using a narrower stance that hits the quads hard)
More deadlifting (conventional and SLDL)
Weighted vest + hills and/or stairs
Not sure if power cleans count as a leg accessory...
As stated above, more squats are usually a good accessory. My accessories usually include Pause Squats, Front Squats, and Stiff-legged deadlifts.
Other tried and true accessories that are less stressful (but still effective) include movements like Glute-Ham Raises and Lunges.
I like doing back-off sets with the same lift. That way you promote hypertrophy in the exact muscles used for that lift.
It depends on what you need to improve your lifts or whatever else you are trying to get better at.
Sometimes it helps to look in the mirror. If your quads are huge and your hamstrings are flat you need to really hit your hamstrings. If your quads, glutes, calves, erectors, abs, grip, upper back, etc. are holding you back than you need to focus on whichever is the weak link.
It could be technical limitations holding you back so you may need to do exercises that improve or correct your dysfunction.
If you have a deficiency in your squats than doing more squats isn't going to help you.
The hard part is finding and admitting what your weaknesses are. It's especially hard if you train yourself.
The best accessory lift is the one you need to get better.
I try to find something I suck at - usually isn't too hard. (Wide stance anything in my case) This generally uncovers a weakness. I totally agree with the notion that doing more squats isn't always the answer - unless it is a technique problem and you know it - and know what you need to correct it. Then "more squatting" is just what you need IF you make the adjustment. Otherwise, squatting more poorly just reinforces the problem. Videos work wonders for this.
Abs and low back work.