Every day spent in the gym is ripe for learning opportunities. We can take much from each day, each set, and each rep; how it feels, what muscles are engaged, what worked, and what didn't. Combining these mental and tactile inputs will build a knowledge base that will increase your level of performance and overall experience. However, sometimes it isn't what we do, it's what we observe others doing. I call this 'Watchful Learning', and it's a great way to add to your workout skill-set.
Watchful learning seems pretty obvious, but it's easy to lose overall perspective at a time when we generally focus on us.
The next time you're resting between sets or waiting on a machine and can't work in, look around. What are others doing? Are their lifts / exercises comparable to yours or is someone doing something different? What do you think their goal is? Also, make note of how people organize their reps and sets. Are they doing 5 sets of 5 reps (5x5), 3 sets of 8 (3x8), 2 sets of 10 (2x10), etc... ? Are they increasing weight as they go, decreasing, or keeping it the same? There are many variables for a multitude of outcomes.
Watchful learning will help with your overall development and provide many alternatives as you progress towards your fitness goals.