The Squat

The basic squat should be a normal part of your routine, since squats tone and strengthen your lower body: calves, quads, glutes, and hamstrings. Improper form while doing squats can lead to knee pain or other discomfort; learn how to do a squat correctly below.

• Place your feet shoulder-width apart or slightly wider. Hold your hands at chest level for balance.
• Bend at your knees and hips, sticking your butt out like you're sitting into an imaginary chair. Keep your chest lifted and your spine in neutral. Do not let your lower back round as you squat.
• Lower down so your thighs are as parallel to the floor as possible, keeping your knees over your ankles.
• Keep your core engaged as you press your heels into the floor to return to standing.
• Do two to three sets of 15 squats.

The Lunge

If you hate squats, chances are you're not a fan of lunges, either. But don't skip out on this move! Along with working your lower body, lunges also challenge your balance and core. When you lunge, make sure that your lowered knee doesn't touch the floor and also keep the upper knee parallel with your ankle, not past it. Here's how to do a lunge.

• Keep your upper body straight, with your shoulders back and relaxed and chin up (pick a point to stare at in front of you so you don't keep looking down). Always engage your core.
• Step forward with one leg, lowering your hips until both knees are bent at about a 90-degree angle. Make sure your front knee is directly above your ankle, not pushed out too far, and make sure your other knee doesn't touch the floor. Keep the weight in your heels as you push back up to the starting position.

Related:

14 Exercises That Will Get You a Better Butt [2]

The Plank

The plank makes you sweat for a reason: it's a great all-over body workout that focuses on building a strong core. Common mistakes people make when in a plank position are rounding their spine or sinking in the pelvis, both of which make this move dangerous to your lower back if you aren't careful about your alignment. Here's how to do a plank.

• Start resting on all fours.
• With your palms flat, raise up off your knees onto your toes. Keep your hands directly below your shoulders.
• Contract your abs to keep yourself up and prevent your bottom from sticking up. Remember to keep your belly button pulled in.
• With your head and spine in line, keep your back flat — don't let it curve. Picture your body as a long, straight board.
• Hold as long as you can. Aim for 20 to 30 seconds in the beginning and work your way up to one minute as you get stronger.
• Lower down to rest, then repeat three times.

The Sit-Up

A classic move from gym class, the sit-up works the abs and hip flexors through a wide range of motion. When doing sit-ups, remember not to lace your hands behind your head, which can put too much pressure on your spine and neck. Instead, place your hands behind your ears with palms facing forward, or cross your arms over your chest, and make sure your feet are planted firmly on the floor. Here's how to do a sit-up.

• Lie on your back with bent knees and feet flat on the ground, and place your hands on opposite shoulders.
• Keeping your heels on the ground and your toes flat to the ground, engage your abdominal muscles, and gently lift your head first, followed by your shoulder blades, coming into a full-sit up position.
• Hold the position for a second, and with control, come slowly back do to lying on your back.
• This completes one full sit-up.

The Push-Up

Push-ups get your heart pumping while working your arms, back, and chest. When my trainer first showed me how to do a push-up the right way, I realized how incorrect my form had been all along. When doing a push-up, make sure your arms are aligned, your belly button is sucked in, and your hands are steady with fingers spread out. Here's how to do a push-up.

• Start in a plank position, with palms spread out evenly and your shoulders over your wrists and legs out behind you. Pull your belly button in, and keep your back straight.
• As you lower and exhale, bend your elbows outward to the sides. Hold at the bottom before you raise back up to complete one rep.

Related:

12 Ways to Push Your Push-Ups [4]

Triceps Dip

Triceps dips are a simple way to tone shoulders and upper arms, but while the move seems basic, it can be easy to do it incorrectly. Make sure you aren't rolling your shoulders forward [5], and don't just lift and lower your butt; focus on bending your elbows and strengthening your arms to ensure you're focusing on your triceps. Here's how to do a triceps dip.

• Position your hands shoulder-width apart on a secured bench or stable chair.
• Slide your butt off the front of the bench with your legs extended out in front of you.
• Straighten your arms, keeping a little bend in your elbows to keep tension on your triceps and off your elbow joints.
• Slowly bend your elbows to lower your body toward the floor until your elbows are at about a 90-degree angle. Be sure to keep your back close to the bench.
• Once you reach the bottom of the movement, press down into the bench to straighten your elbows, returning to the starting position. This completes one rep.
• Keep your shoulders down as you lower and raise your body. You can bend your legs to modify this exercise.

The Bicep Curl

The bicep curl is one of the most basic strength-training moves to master. Make sure you start with weights that allow you to keep proper form throughout your set; if you find yourself swaying back and forth while you're making a curl, try a lighter weight or stand in front of a wall, keeping your back straight while you do the exercise. Here's how to do a bicep curl.

• Start by holding a dumbbell in each hand at the sides of the body.
• Keeping your elbows close to your side, slowly raise the dumbbells to the chest.
• Moving with control, lower back to the starting position.
• This counts as one rep.

Once you've gotten the hang of the bicep curl, try multitasking with lower-body moves (like a squat or lunge) to save time in the gym.

The Overhead Press

Another basic move for your upper body is the overhead press. Standing up while you complete this move works more of your body since you have to keep your core engaged, but if you find that standing is too hard, try doing the exercise while sitting on a chair or weight bench. To start, find two dumbbells that are at a weight you can safely lift over your head for eight to 12 reps (err on the safe side and start with lighter weights until you know which weight is right for you for this exercise). Here's how to do an overhead shoulder press.

• Hold a dumbbell in each hand just above the shoulders, palms facing in.
• Straighten your arms above you.
• Bend the elbows, coming back to the starting position to complete one rep.