Or better still, see if you can get one of those Kylie 'Hot Pants Workout' videos......does wonders for me, haven't lost any weight yet......perhaps it's the bottle of lager that accompanies me on the sofa?
But seriously, I used to be a PTI and for someone who has not exercised regularly the best advice is to take it easy to start with. There is nothing worse than going out and doing 'what you used to be able to do' 10 years ago, achieving it with a bright red face and then spending the next few days hobbling around in lactic acid! The hardest bit is getting through the first month or so of regular exercise, after that the body and mind somehow seem to become a little more accepting and eventually (!!) it becomes good fun and even adictive in some cases.
The comments about aerobic exercise are indeed correct. If you have ever been to a gym you will have seen one of those charts on the wall that shows 'ideal heart rates' for age/ sex etc. They show a maximum heart rate and various 'training zones' depending on what you are trying to achieve. Something like 60-70% of your maximum heart rate is in the very good fat burning area. I would advise building up to that slowly, keeping 'comfortable' for a month or so before you push yourself a little harder.
Variety is also good. We tend to do what we 'like' doing and eventually this can become boring and your body gets so used to it that some of the benefit is lost. So try mixing it up. Jog, swim, cycle, hill walk (one of the best ways to lose weight - spend a day out in the hills with a map and compass and put some weight on your back) as it is constant exercise for half a dozen hours with your heart rate up somewhere like 50% of your max. Vary your running - don't just jog the same route every time. Perhaps jog into the local park and do bench dips on the park bench, step ups on the same bench, get onto the football field and sprint from one touchline to the other (across the pitch to start with!) and then turn round and walk back to recover and then go again. Believe it or not that's called Fartlek training! You can do something similar between lamp-posts etc.
Anyhow, hope that gives you some ideas, remember to warm up and down before and after exercise (that's a whole subject in itself!) and DON'T DO LOADS OF STRETCHING BEFORE YOU HAVE WARMED UP! That's how you pull muscles! Think of the warm-up as getting from sedentary to blood pumping round the body full of oxygen so you are ready to exercise. (gentle jogging, stepping etc etc with increasing intensity over about 10 mins)
Have fun.
PP