I usually warmup by jogging slowly.
For starters, set yourself a target distance.
Each week increase the distance by 10%.
Jog slow.
It is good to plan one of your runs where you emphasise on your
form. In short, a good form is that you "run tall". Imagine a
string pulling your upwards. For more details, pick up a book on
running.
To really burn fats, you'd have to jog more than 30 minutes.
But if you are a beginner, just concentrate on short jogs
first.
Most of all, learn to enjoy it 
