Utthita Parsvakonasana from top.
The tendency is for the bottom buttock to stick out and the top ribs to collapse forward
bring the bottom buttock forward and under.
Spin top ribs back and over.
These adjustments move everything in toward the middle.
Shift the bottom buttock toward back heel, away from the front bent leg. This gives more length to the bottom waist.
Advice on alignment: http://www.yogajournal.com/video/86