One of the more prevalent problems lifters have with their deadlift technique is the inability to get their weight back. This can lead to a few issues, like your weight shifting forward causing you to pull through the toes and not the heels.
The barbell will also "get away" from you. And that's not good.
This results in a poor line of pull where the axis of rotation is further away from the barbell, oftentimes compromising low back integrity. More to the point, the barbell feels like a damn magnet is attached to it.
While some people are more visual or auditory learners, others are more kinesthetic learners. Meaning, in order to understand what their body is doing in space, they may need a little more feedback. This is where using props comes in handy.
I like to use a box to teach people what it means to get their weight back. The idea is to set a box underneath so that when they grab the barbell they have to "sit back" until they feel the box.
It's important to note that this is a "hover," not sitting onto the box with all of your bodyweight. The objective is to maintain tension throughout: no relaxing on the box. Soon you'll be able to properly get your weight back without the feedback of the box. And you'll lift heavier.