You may find it helps to use hair clips or the red sold clips which will hold the potholder and binding together while you sew. May I ask are you using at least a 2and half inch wide binding strip folding in half one and a quarter inch wide . Sew the edges down on the front, press over and down ready to sew.
Some say do a 3/4 inch seam I find on potholder s too large.

My bindings are coming out much better since I have started using the Sharon Schamber method. Here is a link to it on You Tube. You could also do the maching sewing on it I believe.

http://www.youtube.com/watch?v=4PE0Yq9iGlc

I would try a binding a bit larger than you are using now, make sure you trim your seam so its all the same size, and maybe try a bias binding. I hate makeing bias, but when I need to, I make myself. I am always amazed at how smoothly it lays down.

If you are folding the binding to the back and want to machine stitch from the front in the ditch, put pins in through the front vertically to the binding seam. make sure to catch the binding in the back well and it should work. I use at least two ;pins on corners.