1) Form: think of the movement pattern and how your body works. There are no linear movements in the human body. Ask yourself a couple of questions:
a. What is the area that am I targeting?
b. Where is the movement (strength) coming from? Every movement in the human body is in an arc form. There are no linear movements. There will be certain exercises that require either the weight/kettlebell/cable etc. to move in a linear form or have the muscle remain static looking like it’s a linear form. Visualizing the arc will help with your form. For example a tricep extension with a band will require your elbow to remain by your side for the ENTIRE movement. The arc will generate from moving your hand top to bottom. The primary muscle that is activated remains neutral and the hand and the weight attached it is the arc. The contrary is true with a loaded squat. The bar is supposed to remain linear: straight line going up and straight line going down. Your body, in this case primarily your hips will be pushed back and lowered curving at you lower it.
2) The rep scheme: how many reps are you doing? This is critical for either strength or power or gaining muscle size or simply making the muscle stronger
a. Reps of 3-6
b. Reps of 6-10
c. Reps of 10+
3) The weight being used: the first thing I will say is to always lift heavy no matter what rep range. You cannot expect to bench press the same amount for 3 reps as 10 reps, however, the difference in weight will still make it difficult after sets completed. The general rule is simple:
a. If you do your first and reach the end of the rep scheme and couple have done 2-3 more reps, the weight was too light. You should have gone heavier. You’re better off going too heavy for a set and reaching 5 reps instead of 6 to close out the set, then doing 6 but knowing you could have done 10. NEVER waste a set. As for you last set, if you train to failure on your last set, no worries, just lower the weight and finish up.