Do a set using a weight you can lift for 8-15 reps.
Then perform a set of lying (supine) front raises using a weight you can do for 8-15 reps.
The point of maximal mechanical tension when doing front raises is when your arm is parallel to the floor. So when doing the seated raises, the point of max tension is when your arms are perpendicular to your torso. With the lying front raises, the point of max tension is when your arms are parallel to your torso.
Don't read this unless you want to get bummed out about how you've been training the wrong grips, rep ranges, and exercises for your biceps, your back, and your entire lower body.