Start with walking/jogging/biking. Take it as intense as you can reliably handle(be mindful of your heart rate). Do anything you help increase your daily activity, be it parking further away, taking more stairs, casual walks, etc etc etc. Everything counts at this point.
Do you know your BMR? You need to eat at a caloric loss of 500(lower is okay but loss will be slower) to no more than 1000 of your BMR. Consistency is key. Consistency is key.
Consistency
is
key.
That being said(consistency is key, I mean), you have to make small lifestyle changes that you will be able to keep. That means not going overboard and only trying to eat salad or some other "healthy" foods. Restricting certain foods can be helpful, like soda, excess alcohol, and fast food, but make your goals realistic and fitted to you. The only diet that will ever work is one you will stick to, and that means a lifestyle change. Enjoy your favorite dish every now and then. If you eat out just make sure not to eat too much. The biggest thing is calories in and calories out, worry about the types of foods when you are more comfortable with the changes and you become more knowledgeable. The only caveat is you want a good amount of protein to preserve lean tissue.
Also incorporate body weight exercises. This also falls under preserving lean body mass, but also helps to increase your caloric deficit. Don't forget to eat a little more(especially carbs) on days you workout. You may be eating at a deficit, but when you workout intensely, you will drop even further below your BMR which isn't necessarily good.
I got to the point where I lost the point of my message. If you have any questions or want me to clarify something, please let me know! I know a lot of fancy words but if I can't even keep track of my post I can't very well use them now can I?