Legs are a big group of muscles. Which includes muscles i-e Glutes, Quadriceps, Hamstring, Calves mainly. The are used daily intensively while walking, running etc. In order to kick start growth of your leg muscles you have to use more volume and work your legs with different angle.
Barbell Squats :This is the most effective exercise for building Quads. You can do squats with a barbell or smith machine. Hold the bar and position it on the back of the shoulders, then lift it from the rack or smith machine. Bend knees while going down. Keep the back straight.Tip: Your feet and knees hould be pointing in the same direction and keep your back straight. Keep on lowering yourself until your hips are parallel to the floor. Keep a spotter near you if you are a beginner. Now extend your knees lift yourself upwards. Until your body is straight.
Muscles involved: Quadriceps mainly and glutes to some extent.
Lying Leg Curl :
Its very effective in hitting hamstring. Dont put stress on quads only. Building proper shape of hamstring is as important as building quads.
lye with your face towards the bench putting your feet below the lever pad. Hold the grips to fix your body on bench. You should be lying in such a way that your knees are at edge of the bench, to give you a good range of motion. Raise the lever to the back of the thighs slowly and drop it back. Do it for 3 sets of 12-15 reps.
Muscles involved : Hamstring mainly
Standing Leg Calf raise :
Calf muscles are very stubborn and hard to build unless you have good genetics or sincere devotion to build them. Standing calf raises hit them well enough.
Position the barbell on the back of your neck. You can use power rack to set the barbell easily or you can use Calf raise Machine if available in your gym. Stand on the calf block which should be right in-front of you. Tip: Dont lift weight and start walking or you can injure yourself badly. Your toes and balls should be present on calf block and your heals and your foot arches extending off. Raise your heels by extending your ankles as high as you can, stay at the peak for a second and then start declining slowly.
Muscles involved : Gastrocnemius or Calves