Hey there, as I said let's talk about stretching.
But I don't mean when you just arrive to the gym you must do it. No that's not the way. Always stretch when muscles, joints and tendons are hot, that mean that you have to do some light cardiovascular exercises like biking, walking or running a little before stretching.
Best way for this is gradually stretching to a point of tension that we can hold on. You must note that there is a good stretch but you don't have any discomfort. That's the point you must keep about 20-30 seconds. Don't forget feel pain means that you are injuring yourself, causing micro-tears in your muscles and / or ligaments and possibly deriving a major injury.
It's also good do some stretch exercises when finish a set, i.e when you finish your chest reps, do some chest stretching.
That way you will enlarge muscle gainning some elasticity and muscle tone.
You can see a basic stretching routine at image, but I suggest you talk with the instructor and make an specific one according to your possibilities.
Let me know, do you always stretch before doing some sports, playing basketball, or football?
Many more posts to come soon!