Depending on your height will depend how wide take your stance. Your foot should be at a 30 to 45 degree angle to the bar. If it is open too much you will have a problem with your balance at the top. If your feet are too straight you will be unable to get your hips close enough to the bar and will not maximize your leverages.

When you get up to the bar, take a look down. The bar should line up with the front of your quads while you are standing up straight. This is a starting point on how close you should be to the bar. You can also check the eyelets of your shoes. If you need to move closer or further away, start by moving by one set of eyelets at a time. This makes it very easy to duplicate your stance until you are comfortable with the changes.

Your setup for a sumo deadlift will be the same for everyone. You goal is to get yourself in perfect position to squat the weight up. If you have ever box squatted, your form will be the same as your position when you are sitting on the box (that is if your squat form is good). Your knees should be pushed out to the side as much as possible and back arched with your chest up as high as possible. You want to get your hips as close to the bar as you can before starting your pull.

Getting your hips closer to the bar is one thing people miss when pulling sumo. As you start to pull you want to pull the tension out of the bar as you push your knees out to bring your hips closer to the bar. This is what I am doing in the first three pictures. If you jerk the bar or just pull you will end up on your toes or hips will come up first and you miss with the bar getting away from you. Now as your hips are getting closer your chest should come up and you should be trying to drive your traps toward the rear. I would say pulling your shoulders back but you should not be retracting your shoulder blades just yet. You shoulders should be relaxed and almost hanging naturally.

Once you have pulled all the tension out of the bar you should be spreading the floor and driving your traps back even more. This will allow you to use your body weight as a counter balance and if done correctly it will be as if you are falling backward. With lighter weight you might even fall back if you apply enough force to the bar. As you come backward your hips will get closer to the bar and let you use more leg drive all the way to the top. With your chest up already it will make your lockout much easier than a conventional deadlift and take a lot of the stress off your lower back. The last pictures you can see how much I am puling back. Once the bar gets to picture six it does not come up anymore. With my hips moving forward and my torso going backward I lockout the weight without lifting it higher than needed. It is much easier to move things at an angle than straight up. That is why you can leg press more than you back squat.