Lift Your Body Not The Bar
If your upper body is always too tense or stiff, or you pull with your arms, change the way you think about the lift completely:
Don’t lift the bar; lift your body.
Focus on moving your body the way you need to, and the let bar follow.
It’s attached to your shoulders—if you drive into the floor and extend yourself upward, the bar will be accelerated up with you.
Once you can feel this most fundamental element of the lifts, you can start refining the details.
Many years ago I heard Tim Swords say, “Tow the bar”, and I’ve always liked that as a really simple way to think about this concept.
When I was just starting out lifting, I thought about my arms as rubber bands—as I pushed and extended by body, the weight on the bar stretched them longer and longer until I reached full extension, at which point all that band tension snapped me down under the bar.
Figure out the cue or description of this that makes the most sense to you.