There is a common saying in the fitness industry - "If you aren't assessing, you're guessing." I've seen it variously credited to Dr. John Berardi, Alwyn Cosgrove, Mike Robertson, Paul Chek, and others. It's usually discussed in the context of either measuring results or doing movement/strength tests to determine where you are starting from.
My question for today is, what are you measuring in your training? Here are some options.
Weight - Pretty simple - get on a scale at regular intervals and record the results. Know how I know if my bulking plan is working or how far out I need to start cutting for a competition? I weigh myself every day first thing in the morning, and have done so for years. I can tell you what effect my training and my diet is having on my weight.
Size - Take measurements. Find a consistent plan or make up your own, and take those measurements regularly. I do mine - shoulders, chest, biceps, forearms, waist, hips, thigh, calf - once a week. I do hip and waist daily when I weigh in. If your goal is to gain size, this is a good one to do. It's one thing to have anecdotal evidence ("I think I look bigger") but another to have real evidence ("I've added 0.25" to my thighs, 0.5" to my biceps, and 0.25" to my forearms since I started my hypertrophy program").
Weights Lifted - Are you lifting more for the same reps in the same exercises? You should track this no matter what your goals are. A training log isn't really optional, even if you only track your main lifts.
Reps and Sets - Did you get more reps for the same weight? More sets than last time? You can make progress but unless you track it, you're guessing and trying to remember instead of following a systematic approach.
Kcals - Seriously, it's a pain in the rear end but things like Fitday do make it possible to do this. If your goal is body-composition related, you can track this.
Any others? I do all of those (I log my food, track my gym progress, measure weekly, and weigh daily). What do you do, and what did I miss on my list?