I had a similar weight/body shape and am also aiming at around 40 lbs total to lose. I've lost about 20, and I'll probably want about 20-30 more to go. What helped me the most is changing my diet. One of the biggest things is what you drink; you'd be surprised on how many calories you ingest on fluids alone. Cut out soft drinks/a lot of juices (most juices are about as many calories as soft drinks, but with a little vitamin c thrown in).

My weekday meals consists mainly of the following: A small bowl of cereal in the morning (total for me since it's fairly nutritious for cereal) with skim milk, some coffee, and a multivitamin pill, a sandwich with a side salad for lunch, and grilled chicken with brown rice and mixed vegetables for dinner with milk. For the weekends, I usually pick one day to really enjoy something (a Pizza/greasy burger and fries/whatever), but I don't make it a point to eat as much shit as possible just because it's a more lenient day, because at the end of the day you're just setting yourself back the more you eat. If you still feel full by your next meal, you probably ate too much last meal or are eating your next meal too soon. Also, make sure you drink enough water throughout the day; the more hydrated you are, the easier/safer it is to exercise and the more weight you will lose.

As far as exercise, I run about 30 minutes a day, but have been increasing the intensity as it becomes easier. I used to struggle with 6 mph (3 miles), but now am running at about 7.5 mph (3.75 miles). I get up early to do it since it helps wake me up and feel refreshed, and I know I won't do it after work (too tired). The best mentality to get started is that whatever your doing (eating/exercising) isn't the first time your doing it, you have been doing it everyday for the past year and it's part of your normal everyday schedule, that helps me anyways.

Anyways, this isn't meant as a "You need to do exactly this" kinda guide, but it's what I've done and I've been pretty successful with it.