Position back foot with toes facing down on the bench (this will help target the front glute/hamstring more; prop back toes up if you feel too unstable). Make sure pelvis is tucked before lifting the bar (overhead weight makes it harder to use your abs, so make sure low back isn't arching). The wider your hands are on the bar, the easier it is on your shoulders. As you lunge, keep weight in front heel without knee dropping inwards. Back shin will go back towards bench as you lunge.