Before you even approach the bar, you need to be visualizing what's about to happen. Go through some of the points given above and really focus on the ones that apply specifically to you. I know the two main points I need to focus on are keeping my chest up and forcing my knees out. Everyone is different, so focus on the ones that apply to you.
As you approach the bar, get the hands set exactly where you want them. As stated before, the closer you can comfortably get them to your shoulders, the better. Next, wiggle underneath the bar and pull your shoulder blades together and get tight. This is giving you that nice shelf the bar can rest on.
Move your back up and down on the bar until you find that place where the bar feels perfect. Once you hit the spot, make sure your chest is up and the bar is locked in where you want it. Take a big breath and press the feet through the floor to unrack the weight. Don’t set the racks up so low that you have to do a good morning! Before you walk out, let the plates settle for a second.