If you you're a beginner you can get some great information and advice about how to execute the squat and deadlift with perfect form from many different sources.
If you're solid on the basics, IME the best approach is to learn how to listen to your body, developing a mind body connection with how you best move the weight.
Here's a few things I personally keep in mind when working on my setup, technique, and execution of the squat and deadlift.
Back Squat (low bar):
- Bar placement
Where on my back does the bar feel the most secure, while allowing me to execute the lift with the desired technical form? Having the bar placed just a little too high, creates a tendency for flexation when the weight is near or at maximal loads. Place a little too low and it feels like its going to slip of my back. If placed just right, I'm able to push maximal loads with little to no form breakdown.
- Foot placement
How wide should I place my feet to ease the transition to proper depth while providing a solid foundation to push from? I have recently changed my feet width to just outside the shoulder. I used to squat with a slightly wider stance but after some experimenting, I found a better foot placement to meet my needs. I easily get rock bottom depth and I'm able to explode out of the hole.
- Decent
I initiate my descent with both my hips and knees simultaneously. Most beginners are taught to push back with their butts. I did the very same thing when I first started but learned this wasn't the best for me. IME, pushing the hips back promotes a forward push when coming out of the hole, which gets the weight forward and creates a tougher lift. When under maximal loads, you want to be efficient, not create more work for yourself, not to mention increased risk of injury.
-Chest up
I have to constantly remind myself to keep my chest up and not let the weight push me down, creating a slight and subtle hunch. IME, this cue is most important entering and exiting the hole. It keeps my center of mass centered and balanced, allowing me to set up and execute the explosion out of the bottom. IMO, it is the center piece to a well executed lift - do not overlook it.
If all the above is on point, I should be able to execute a near perfect squat - confident decent speed and solid posture, easily hitting depth and exploding to the top, without pitching forward and without flexation.
Deadlift (conventional):
- Foot placement
In this case it relates to the distance from your body, more specifically your shins. IMO/E, this is the most important aspect to the deadlift because it can make or break you - literally.
Being too far away or being too close to the bar can create inefficient bar paths. As you near maximal loads or become fatigued, this inefficiency will readily exploit weak points that could lead to injury.
A great way to determine your bar placement is to document what direction the weight first moves when you initiate the lift. If it moves away from you, you're too close. If it moves towards you, you're too far way. Your goal is to determine the correct distance from the bar, for the weight to move straight up.
-Body placement
How do I position myself for the best force production while staying safe? I like to get my body right over bar, placing my shoulders in front of the bar and high hips, locking my lower back. I don't squat the weight. I envision the movement as straightening of a bent line. Unfolding. Standing up.
I see a lot of people in gym trying to break inertia by squatting down and essentially sitting behind the bar. What happens is their butt shoot up, the weight pulls them forward, and then they're able to complete the lift. IMO, this method is so completely inefficient and a huge waste of resources. I find it interesting how the weight shows them exactly where they need to be yet they fail to recognize it.
My point is, if you listen to your body in relation to the weight and document it with video, you'll be able to identify your individual set up that will put you in a great position to be strong and healthy while performing the deadlift.
Its really late for me so I hope this makes sense and assists you in some way shape or form.
