My new Craftsman gas lawnmower won't restart?

I've had this two weeks and it was starting easily and working beautifully. It has gas and oil and the grass catcher is emptied out.
I was mowing and all of a sudden the engine just stopped.
I thought it had run out of gas; I added a little and it still wont even turn over.

I have virtually no mechanical knowledge or experience and dont know where to start with a problem. Do I have to take it back to Sears? What things can I check? I don't want to get too deep into it, but if there are a couple of fairly simple things to look at please let me know