I quit smoking, I gained weight, now is time to lose the weight and all I have is a treadmill. What is best?

How can I best utilize the treadmill to get the most results (other than plugging it in and jumping on). :) I have upped the water and fruits and veggies, but I know I need to move more. Do you have any tips? I am ready for this, like I was ready to quit smoking, and I am tired of the extra weight. (30 lbs. in 2 years) It is getting too chilly out and dark too early when I am able to go for a walk outside. Thank you in advance.