Basting is a method of holding the three layers of a quilt together while you do the actual quilting. It can be sewn, pinned or spray basted. Here is a link with more info.
http://quilting.about.com/od/quiltba..._the_Quilt.htm
Stitch in the ditch means to stitch in the seams between two pieces of your quilt.
http://quilterpenny.wordpress.com/20...-in-the-ditch/