i was just doing some squats today and i got a little confused as to how i'm supposed to position my hips and lower back when executing the squat.. the minor strain in the right side of my lower back i'm feeling now is making me wonder if my form is proper or not..

when you have your legs spread, the bar on your back, and you're ready to go into the squat, do you flex your hips forward hard (kinda stickin your butt out) and maintain that flex for the whole set? i'm thinking maybe i flexed it too hard, and going down like that puts a lot of strain on the lower back.. but i'm not sure if that's how its supposed to be.. i'm pretty new to squats.

i looked at a few technique explanations and they didn't specify too much about how much your hips should be flexed and all... anyone got the proper fix on this?