Find a stable platform to elevate your front foot on. Place the front half of your foot on the platform, push through the calf to raise your heel, then lower yourself until you feel a deep stretch in the calf. Keep your knee straight in the working leg.
Place feet hip-width apart. Lean forward maintaining a slight bend in the knees and drive your hips back as far as possible, while maintaining a straight back. From there, squeeze your glutes forward to get back upright. Keep the weights (dumbbells or barbell) close to your shins at all times; don't let the weight drift away.
Place feet slightly apart, then take a step forward (position in video). Staying upright, bend at the knees until your back knee touches the floor, then push through both legs to get back up. Maintain tension throughout, whether you are at the top or at the bottom of the split squat.
Elevated your feet on plates if you can perform this with more range of motion.
Stand with heels hip-width apart, heels elevated if necessary. Bend at the knees and hips and squat down slowly as low as possible while still maintaining tension and a straight back, then stand back up.
Barbell back squat: Grip bar with hands just outside your shoulders, placing the bar on the meaty part of your upper back. Squeeze your back and make sure the bar stays firm against your body, then un-rack. Step back and perform your squat. When you re-rack, make sure you hit the bar fully against the rack before lowering it into the J-hooks.
Goblet squat: grip kettlebell with both hands, keeping it close to your chest.