how many warm up sets/light do you do before the heavy set /failure one?
Depends on the exercise. Many times for a body part the first exercise I use needs a warm up then the subsequent exercises doesn't need it. Below is today's work out. I admit I would be better off with more warm ups. I do the minimum I can so I can really hit the real work set. Warm us should be easy and non taxing. I know Yates was criticized for for not calling counting his warm up sets but they were non taxing. He did something like this for his inclines. Set one: 1 x 8 135. Set two: 1 x 8 225. Set three: 1 x 6 315lbs. Then the real set was 1 x 8 with 415lbs. Even Yates said on tape that sometimes when he gets to exercise two or three for a body part no warm up is needed.
Leg press 1 x 13 (two prior warm up sets. One warm up set to 12 and the second warm up with increased weight is one set of 8
Dumbbell squats 1 x 12 ( no warm ups sets. I'm sweating and breathing like a race horse after that one set to failure leg press.
Stiff dead lift 1 x 8 (One set of six for a warm up with a lighter weight.)
Leg extension 2 x 23 ( No warm up)
Standing leg curl 1 x 15 (No warm up set)
Single dumbbell side bend 1 x 18
Hanging straight leg raise 1 x 25
Hip ups off the floor 1 x 25
Standing calf 1 x 20 ( no warm up)
Seated calf 1 x 19 (No warm up
Neck one set of each side (One warm up set for around 8 reps. The one work set per side is around 20 reps with increased weight.