Okay, first things first [DISCLAIMER]: I am NOT a professional, personal trainer, or a physician- these are just things that I do. Consult a physician before starting any exercise program and all that jazz.
Here's the basics of a work out: warm up, stretch, work out, cool down, and stretch.
HERE IS WHAT I DO
I like to do cardio first, then weights of some sort. I usually "run" (jog/walk) a mile and then walk for cardio and then either upper body or lower body. A lot of people do chest day, leg day, arm day, et cetera. I just do upper body and lower body because I'm cool like that. I try to work out all the muscles on the top/bottom each time. Except maybe those ones on the face in this pic:
It can be kind of hard to do certain stretches or lift weights when you're bigger. My stomach can get in the way sometimes, that's for sure. There are plenty of resources online to help you figure out how to work out at any size, as well as personal trainers, coaches, and doctors. I have a tendency to really push myself, both physically, mentally, and emotionally, so I'm hesitant to give advice because it could possibly get you hurt. I come close to hurting myself sometimes, which is why I force myself to take rest days. Exercise is important, but you can't be active if you're injured.
The important part, to me, is to make it fun. If you make it work, you don't want to do it. I have Zumba Fitness Core for the Kinect and dance workout DVDs, as well as take dance classes. I like to run on the treadmill because I enjoy it, some people like to run outside (I don't). I like the weight machines at the gym because I'm too lazy for free weights and I like the gym because that's where I'm most motivated; in my own home, I don't want to do anything. To each their own.
I hope that helped a little!
<3 - CFC