Diet and exercise plan

Why am I not committed to losing weight?  What is really wrong with me?  Now I do know the answers to those questions.  I would have already answered my own question by this point.  How do I finally plan to exercise?  Do I walk five days a week for 20 minutes?  Six days for 30 minutes? Every day for 45 minutes?  I wonder if I should exercise based on my body type.  Should I also exercise based on where the fat is stored?  It is as if I have a lot to think about and plan.