deadlift bar path, press help

[jnghnl]

1. when the bar travels up during the deadlift, the bar is supposed to stay in contact with the thighs, and go through a vertical bar path, right?
but when i deadlift with lights weights the bar goes like this from the bottom up : up up up (bar crosses the knees) behind up up
the bar goes straight up until it clears the knees, but after it clears the knees it immediately drifts behind toward the body about an inch, and then as i open my back angle it goes forward again and eventually ends up over the middle of the foot at the lockout. and when the weight gets heavier, i fail to press the bar against my thighs with my lats and the bar leaves contact with the thighs. so i was wondering : is it possible to keep the bar in its ideal vertical path while keeping it in contact with the thighs at the same time? for me it's either the path is vertical but forward of my thighs, or the bar in on my thighs but the path is not vertical.

2. another quick question on the the press. are you supposed to squeeze your glutes during the whole duration of the press? or only when you lay back? or not at all?

[Mark Rippetoe]

1. How do you know that's what you're doing? Have you made a video? Post it.

2. Don't think about individual muscle groups when you train. That's bodybuilding.