Help with excercises

What are the most effective excercises to do to firm up your upper arms and thighs? I am sure they are going to become flabby once I lose some weight( upper arms already are flabby) Please help! I am having my surgery this Tuesday.

 Hate to tell you this, but there is nothing you can do to make your skin bounce back.  You can firm up your muscle tone so that there is less skin hanging.  How your skin bounces back is a factor of your age, sex, if you smoked and genetics and other things you can't do much about right now.  

Exercise is always a good thing - so don't forgo it, but its not going to take the place of plastic surgery or self acceptance.  

You want to design a good overall exercise plan that incorporates cardio and weight training, targeting all the muscles in your body.

The core is very important as it is what supports your entire body.  Yoga is a great core strengthening workout.  Anything that gets you breating hard and sweating is good cardio-running, speed walking, hiking.....

For weights, you want to use higher weights and lower reps to build muscles.  Never work the same group of muscles two days in a row-you need a day of recovery in between. 

I use P90X for weight training and I also run, hike and do yoga.

The key is to find things you truly enjoy so you'll keep doing them, and keep mixing it up....keep your body guessing what is coming next.  You can't fix the skin, but you can improve how it looks with good muscle tone.