You should be gripping slightly more than shoulder width wide.
Source: My g/f who's a physical therapist and deals with shoulder injuries, etc. I've asked her this question while she watched me do a shoulder press and told me my grip of shoulder width was too narrow. I moved it past shoulder width about 2-3 inches and she said that was correct. May result in wrist pain if you form isn't great. I haven't watched the Rippetoe video's in a while, so I can't totally recall where he placed his hands on the bar.
Do the shoulder press movement without any bar. Just let gravity show you where your arms will move with zero resistance starting with hands extended overhead. Exagerating can help by pushing the elbows way to the back on the way down. Pay attention to whn your should socket joints start giving resistance.
Hands in/out matters less than getting those elbows forward till your upper arms are parallel with the ground. It's similar rational as to what proper bench form is and why you lower the bar to the nipple.
Sixguns,
Those Rippetoe videos on YouTube are priceless. As are the videos that come with his book if you can still find them (a popular web site is currently down). I think he spends 20-40 minutes just explaining and demonstrating proper form in the videos that come with the book.
You don't have to drop weight alot. Just deload 20-30 pounds. Pay attention to form while thinking of the minutia in the videos. Eventually you'll pay attention to all of it.