You can do it a number of ways. 1st off don't rough it out with a roughing gouge just yet. You'll end up splitting the corners off. Start by making either a v cut or a cove cut where you want the square shoulders.
Here is a video on cutting a cove with a spindle gouge. It is the same technique. don't use the scraper as I show in the end of this video.

If you need square shoulders use the toe of the skew similar to cutting a V cut. You can see how the v cut is done in my skew practice video.

If you sneak up on it you might be able to do it with a parting tool however it would be really easy to chip the corners.
Once you have the corners cut clean the you can rough turn the rest of the piece and then final turn it.

 

Can also cut all four corners with a back saw like Norm does to prevent tear out on square ends.

 

Jeff,
In addition to John's videos, here's a link for an article on cutting pommels.
http://americanwoodworker.com/blogs/projects/archive/2009/08/17/perfect-pommels.aspx
Mike Hawkins

 

Huge help you were. I never even heard the term pommel let alone how to properly cut one. I've been trying but it takes much practice and a new look at proper sharpening as well.

 

I used to use the backsaw to cut my corners but it leaves such torn grain and it's very hard to sand out. Sneak up on the corners with the rough out gouge always cutting away from the corners and using a bevel rubbing cut, not a scrape. Then when you get close you use the parting tool if your more comfortable with that. It doesn't leave as good of a finish as the skew but it's better than the saw if you take light cuts.

 

Norm Abrams been notching corners of square end of spindles (table & stool legs and other turnings) with backsaw for couple decades before turning to avoid tear out. He has gone back in and used skew, gouge, or parting tool to clean up transitions too!

Not saying only way to avoid tear out on square end of turnings!!

 

Let me say I love Norm. Watched his show every Saturday for many many years. In fact I built a Norm Abram rocking horse for my son's 1st birtday 21 years ago. I think I learned to use the saw for cutting pommels from either his show or magazines. It does work. However In the early shows he is not a skilled turner. I have watched him improve over the years along with the other TV woodworking hosts and I guess myself as well. Since I started turning mostly and don't make much furniture I think my turning improved faster. Still love to watch their shows and learn something every day.

 

One thing you may want to do to insure it is mounted square is to make a very small V cut (in the waste area) with the point of your skew. Then stop and check it, very often only two corners will have a notch and you have to adjust the mount slightly.
In the article linked by Mike H., the author shows the bevel of the skew perpendicular to the work, not the handle. You can also use a spindle gouge with the bevel perpendicular; the curvature of the blade will clear away the waste wood.

 

Making a pommel

This forum is terrific. Not only did I discover the basic possible solutions to my question but also a reminder that sharpening is something I need to take a closer look at. I tried making a rounded edge skew chisel out of one that I had but it didn't cut the butter. I don't have the grind just right because I get a half inch in from the corner and it doesn't want to go any further when I go after a :smileommel. I can relieve some of binding on the chisel by cutting away at the waste but I'm still practicing. Most of all thanks to everyone who has expressed their various points of view.