Position body under bar, and place bar on upper back (trapezius). Stand with one leg forward, with front knee directly over ankle, and knees slightly bent with feet approximately hip width apart. Keep back heel up and toes pointed forward. Stand in good body alignment (abs tight, chest up, back straight). In a controlled motion, lower body by bending knee and hip, keeping back straight and maintaining good body alignment. Keep knees in line with toes; avoid turning knees in or out. Keeping forward foot flat on the floor, continue lowering body until just before back knee touches ground, without compromising form (back straight, abs tight, chest up). While maintaining controlled motion, pushing with front heel, return to starting position (avoid locking out knee). Do not allow muscles to relax before next repetition.
Here are a few suggested alternative exercises:Ball Leg LungeBall LungeBall Wall SquatBand LungeBand Lying Leg ExtensionBand SquatBand Standing Leg ExtensionBarbell Bulgarian Split SquatBarbell Lateral LungeDead LiftDumbbell Dead LiftDumbbell Hack SquatDumbbell Lateral LungeDumbbell LungeDumbbell Lunge CrossoverDumbbell Lunge WalkingDumbbell SquatDumbbell Sumo SquatFront SquatHack Front SquatHack SquatLeg Press - MachineLunge - BarbellLunge - Smith MachineLunge BackwardLunge CrossoverLunge DiagonalLunge ForwardSquat - Barbell