I used to log all my workouts and compare to the previous year, it was more about strength. Tracking the big 3 lifts and my other favorites.
These days i just go by how i look in the mirror.
If you're into strength training, i would record all your workouts and compare every 3-4 months. Make sure you are making at least some progression. Track your bodyweight too.
Take pictures every few months. Make sure you take the pictures in the same location as lighting and distance can make you look much different. You should be able to notice some good progress on the 6 month spread.
You won't notice on a daily basis, that's why you need to track workouts and take pictures. You should be able to see a substantial improvement in both every 4-6 months if you are training with intent and eating well.
Every month i take some pictures just to track progress. Sometimes i don't think i've changed much until i look at a picture that's 6 months old.
I also think it's important to get lean once a year for a month or two, that's the best way to see how much you have grown.
