The Key to Big Legs
Going heavy on compound movements then using isolation is the winning formula. After stretching, and warming up, go heavy within a set rep range (5-20) for 2-3 working sets on back squats, front squats, hack squats, or leg press. After that, move on to a single leg movement like lunges, step ups, or single leg press, leg extension, or leg curl. Do that for 3 sets of 10 reps going heavier every set. Then finish off with isolation movements. Do leg extension and leg curls with progressively heavier weight for 3 sets of 20 reps. If calves are a weak point put them first, you can also have them at the end if they're not as much of a weak point. Do standing calf raises for 4 sets of 20 reps with increasing weight.
This protocol will ensure you're breaking down your legs maximally to allow for the best recovery and growth. To keep it going over time, make sure you're increasing the weight you're using on the heavy compound movement.
The results will be stronger, bigger legs over time.