There is nothing like a nice set of wheels. A tough body part to build but if you work hard the results are amazing, the legs respond best to heavy compound movements like the squat.
The upper leg muscles consist of;
Quadriceps : These are the large muscles in the front of your thighs. They extend your leg.
Hamstrings : The hamstrings lie along the back of your thighs. Its very easy to pull them unless you warm up fully and stretch them properly before doing any strenuous leg exercises.
Developing large powerful leg muscles require heavy compound movements such as the classic squat and the leg press.
The legs require a lot of hard work to bring them up to scratch but they do tend to respond well to exercise so its worth it in the end when you have large defined leg muscles.
The legs make up half of your body so they need regular attention and also being a large muscle group they need longer rest time than smaller muscles in order to recuperate.
IMPORTANT : always be sure to warm up and stretch your leg muscles well before giving them a workout, its very easy to pull a leg muscle and a little precaution before working them will be worth it. Also regular leg stretching is good for their flexibility.
10 minutes warming up and 10 minutes stretching would to the trick.
Here are the top exercises for the Leg muscles
The squat is one of the best exercises you could possibly do. The squat is an incredible overall leg mass building exercise and you should definitely include it in your leg workouts.
Face the barbell on the rack. Step under it so that the bar is resting across the back of your shoulders and on your trap muscle. Raise the weight off the rack and step back a step or two to clear the rack.
Keeping your head up and your back straight lower yourself down until your thighs are just below parallel. Push yourself back to the standing position from that point.
Always have a safety precaution in place when squatting, like a safety bar on either side to prevent you getting trapped under the bar when difficulty arises. Preferably work with a spotter when squatting also.
Variations include smith machine squats.
Front squats place extra emphasis on the outside sweep of the quadriceps.
Cross your arms under the bar and have the bar lie in the front across your shoulders with your arms supporting it.
Raise it off the rack and step away. With a straight back slowly lower down to just below parallel, stop and push yourself up again.
Hold a dumbbell in each hand and stand up straight. Take a step forward with one leg. With your weight on the front leg slowly bend your knee and lower yourself so that the your back leg is almost straightened.
Push yourself back up to the start again and bring your feet together, repeat for the other leg.
Variations include lunges with a barbell across your back.
Stiff Legged Deadlifts
This variation on the deadlift works the hamstrings and also the lower back. Hold a barbell with your palms facing you. Stand up straight with the weight.
Keeping your back straight and a slight bend in your knees, bend forward at the waist until your upper body is almost parallel with the floor. Stand up straight again keeping your back straight the whole time.
You will use less weight in this exercise than regular deadlifts because your legs wont be helping as much.
Hamstring (Leg) Curls
This exercise works the hamstrings at the back of the legs.
Position yourself on a leg curl machine. Place your foot comfortably under the pad. Curl your legs as far as you can. Squeeze at the top of the movement and return slowly to the beginning.
There are literally dozens of different leg press machines out there. But when it comes down to it they all perform the same basic function. Leg presses allow you to work the legs with very heavy weights without the added pressure the squat puts on the body.
Position yourself on the machine and place your feet comfortably on the foot stand. Push the weight forward until your legs are fully extended. Stop, then lower the weight back to the starting position, repeat for the next rep.
Variation include leg press machines that you start of in the extended position, with those simply lower the weight slowly and the push the weight back with your legs to the starting position.
Remember, be sure not to lock your knees when your legs are fully extended as this puts pressure on the joint and could cause an injury.