Aside from exercise routines, how can you benefit from a personal trainer?

Be careful. If you are female aerobic exercise is really not your friend. Stress responses lower estrogen levels and the stimuli for ovulation (fsh). Our society pushes aerobic exercise on everyone. It does not control or aid in weight loss. Resistance training in a non aerobic way is good. If a trainer will teach this it may be good to have a coach and motivator. Read "slo burn fitness revolution" hahn.