
LOL @ Grumpy..
I just got finished mine. So its fresh.
For me, I ensure that my form and pace is correct while doing reps. I work with a personal trainer who also lives in my head for my other 3 workouts per week yelling at me when I go too fast. LOL!
I honestly do not think that the majority of people really know how hard to push themselves unless they do work with a personal trainer who can push them to their limits. I've been working with her for 6 months and its only been within the last month or so that I push myself as hard or harder than she pushes me. I see a lot of people at the gym who do not have the proper form when working various machines, I see them going so fast and "short" that I wonder if its a specific technique and wonder how it can be actually working the muscle completely, and I can only imagine that their performance suffers. But I'm the fat lady at the gym, so I'm not about to make any helpful suggestions. 
During my workout, I push on the reps until I the last 2-3 cause me to feel like I'm going to drop the weight, or I don't feel like I can finish, or if I'm with my trainer I curse her out. I feel the burn in the muscle, during the last set, I'm usually shaking and really pushing it out.
I expect pain and soreness for 1-2 days afterwards. I also expect progression and get it!
SW: 235
CW:220
Rough start due to major carb WD.
MWF: 1 hour run/walk, 1.5 hours in the gym - upper/lower and core
Sat/Sun=Yard/house work, chasing kids, playing
Family walk every night instead of everyone vegging in front of the TV
Personal trainer to build muscle mass & to help meet goals