Barbell should sit across the front of your shoulders
Don't grab the bar too tight as this will reduce flexability
Lunge forward whilst keeping your core braced and your torso upright
Your foot should land with enough distance forward to allow your opposing knee to go directly down (your knee, hip and shoulder should be in a straight vertical line)
Your knees should not track inwards
Just before your knee hits the floor, squeeze your glutes then press back up
Before you finish the lunge, go back down for another dip