Many people are scared to injure themselves while performing the deadlift because of improper form and technique. But, this doesn't mean that you shouldn't deadlift! It is an essential lift and movement to getting stronger and being able to build strong back, lower back, glute and hamstring muscles. Below I have created a diagram of a good and bad starting position for your deadlift.
Let's discuss what is going on in the two images. Firstly, the deadlift is naturally a hinge, meaning that you are bending at the hips to pick up the bar. Secondly, in both images the back is flat and there is no rounding in the lower or upper back. This is a good thing! But that does not mean you are performing the movement correctly.
The differences between the two is the positioning of the hips and torso. On the right, the hips are very low as if the person is "sitting" into the position. For a deadlift, this is not the optimal position to lift as the bar will not travel straight up and down as it should. On the left, the person has their hips a little higher and their knees are pushed back. The shoulders are over the bar. When the person on the left picks up the bar, this is the best position as the bar will travel straight up and down. They will not run into the problem of hitting the knees on the way up.
With that being said, always maintain a flat upper and lower back. Do not shoot your butt up too fast as this will cause your lower back to round. Keep the shoulders over the bar and make sure the bar goes straight up and down.