It doesn't matter whether we're talking about deadlifts, squats, swings, etc. One cue that has made a world of difference for me is to PUSH THE FLOOR AWAY WITH THE LEGS.
In deadlift and squat, many clients think of just standing up. Or in deadlift, they think of pulling with the low back. Thing is, that rarely gets them using the legs at full capacity. The legs aren't engaged much when they should be 100% engaged.
Instead of just trying to stand up, actually push the floor away from you with your legs. This makes these movements somewhat like the leg press but what you'll find is the movements are MUCH more powerful, they're safer because you aren't straining the low back, and you'll likely be able to do more weight.
One problem is that pushing the floor away vs. pulling with the low back in deadlift or just standing up in the barbell squat doesn't look any different. There isn't a visual difference usually except perhaps for a more powerful hip thrust with the push-the-floor away technique. So people can't see a difference, therefore they think their isn't one.
This is where FEELING comes into play. You can easily FEEL a tremendous difference between the two. So focus on that push and you'll make much better progress.
Have a good weekend, folks!