Your legs are, arguably, the most important appendage in your body. I mean, they are how you get around! The entirety of your leg also contains the largest muscles in the body and it is the most powerful limb. You can move a lot more weight with your legs than you can anything else.

Unfortunately, a lot of people neglect their legs when they first start working out. For bodybuilders, this is devastating because they quickly realize that they'll have to play catch-up before they are fit to compete with more experienced lifters. This could shave a year or two off your career! Many inexperienced or foolish weight lifters will have "chicken" legs and a highly disproportionate upper body. If competing in sports, this can affect your balance and have a negative impact on your power.

Those that work out their legs early on will have significant advantages over people that don't. Exercising your legs is one of the quickest and most effective ways to gain mass and strength. Some leg exercises are so strenuous on your body that they will release hormones that cause other muscles to grow more quickly. Not working out your legs can reduce your overall gains by as much as 30%!

For simplicity, I will be including the gluteus maximus with the legs, although it's technically a hip muscle.

Quadriceps: the quads are the most massive and strongest muscle in the body. Their main purpose is to extend the knee from a bent position. These are primarily used when lifting heavy weight off the ground with your legs.  The quadriceps can be hit from a variety of angles, which makes them one of my favorite muscles to exercise.  It's always good to switch stuff up.

Hamstrings: the hamstrings are the main flexor muscles of the knee, which means they are used to pull your foot toward your glutes. These are located on the back of your thigh and are also powerful muscles, although they aren't quite as strong as the quadriceps.

Gluteus Maximus: the glutes are actually an extensor of the hip, but I prefer to throw them into the group of muscles associated with the legs. These muscles are used for thrusting your pelvis or thighs backward and are a very powerful muscle. Believe it or not, most of the power of a punch (if executed correctly) comes from the glutes.

Hip Adductors: these muscles are generally concerned with the lateral (outward) movement of the thighs. What I mean by that is that they are used to swing your leg out to the side and back. These are not the most practically useful muscles, but they are commonly injured and should be strengthened to help avoid injury. If you've ever pulled your groin, then you probably injured these small muscles.

Squats: These are the main quads workout and they do the job very well. Squats are a very difficult exercise to do and it is important that you work with a weight with which you are comfortable. It's very easy to injure yourself if you don't know what you're doing. Don't let that dissuade you, but you should work on your form with just the bar or less than a hundred pounds when starting out. Don't worry, you'll work your way up quickly! When doing squats, make sure you go down to parallel and keep your back as straight as possible. You'll have to learn forward just a little bit to keep your center of gravity, but don't over do it. Squats also place significant stress on the spinal erectors and glutes.  This is one of the best ways to add raw mass to your legs.

Leg Press: The leg press stresses the same muscles as the squat, although it doesn't place any stress on the spinal erectors and places less stress on the hamstrings than the squat does. This exercise, in general, is inferior to squats, but it does have its merits. The odds of hurting yourself are significantly lower and you can isolate the quadriceps more effectively.

Machine Leg Extension: This is really the only quad isolation exercise worth mentioning. Be careful with how much weight you use on this exercise because it places a significant amount of stress on your knees. This is a good exercise for creating separation throughout the entire muscle and will build good mass after you have a strong core set up.

Barbell Lunges: I can't stress enough how important it is to use proper form when doing this exercise. If you go down while in the middle of your range of motion, it's almost guaranteed that you'll twist your knee and tear it to pieces. You should work at about 50% of what you squat for reps when doing these and you should always have a spot behind you. With that in mind, these are fantastic exercises the work the entirety of your quads. The back leg receives stress on the top of the quads and the front leg receives stress on the bottom of the quads. This exercise builds great separation and is excellent for power and strengthening.

Front Squats: Front squats are almost identical to normal squats, but the weight is held across your neck and supported on your deltoids. This isn't the most comfortable exercise, but it's fantastic for building mass near the base of your knee.  This'll help prevent your legs from becoming to large at the top and small at the base.

Leg Curl: There are many variations of the leg curl, but it's main use is to stress the biceps femori muscle in the hamstring muscle group.  This is a good exercise, but is similar to the leg extension in that it puts a lot of stress on the knees.  Make sure you're comfortable doing this exercise and go up in weight slowly.  You don't want to damage your knee!

Cable Kick Back: This is a good exercise that is used to stress the glutes and the upper portion of the hamstrings.  This is a great for creating separation in these muscles and building overall mass.  The only problem is finding an ankle strap to use when at the gym.  I don't see many lying around, although you can probably buy and bring your own.

Good Morning: The good morning is an underutilized exercise that is mainly used to build up the spinal erectors.  If you keep your legs straight, however, you'll place significant stress on your hamstrings and will be able to build them up nicely.  If you do bend your knees, be sure not to extend them as you're returning to the upright position, since you run the risk of injuring your lower back.

Stiff Leg Deadlift: This is similar to the good morning in that its main purpose is to work your spinal erectors, but it's also one of the best compound exercises for working the hamstrings.  This lift places so much stress on your body that it'll release additional testosterone.  This'll increase your gains over all muscle groups, not just the legs.

Most quad workouts will also place a lot of stress on the glutes. Slight modifications can shift significant portions of the stress onto the gluteus maximumus.

Reverse Hyper Extension: This is a bodyweight exercise that is fantastic for building up your glutes. Instead of lifting your upper body up, you make that part static and lift your legs up. This is a great exercise for building mass and separation in the glutes. You can add weight, but it's difficult to control it with your feet.

Lunges: You can modify the length of your lunge to put additional strain on your glutes instead of your quads. If you want to do this, take a longer step forward. This'll place additional stress on your glutes and is great for building up strength in them.

The adductor muscles, like the glutes, are stressed in a lot of the same motions as the quads. The squat does a great job of building them up, actually.

Cable Adduction: This is really the only adductor workout. It puts a ton of stress on the adductors and is great for strengthening them so you can avoid pulling your groin when doing squats or engaging in other athletic activities. You won't gain much mass from these, though. Again, the hardest part if finding an ankle cuff to use.