The cheapest way to get a new smartphone

The smartphone market is a bit of a blur to me, with deals left, right and centre and lots of different ways to pay. So what is the cheapest way to buy a new one?

Apple fans will be well aware of the rumours of the new iPhone coming out this September, but when buying a new phone is it cheaper to sign up to a contract or get a sim-only deal?%VIRTUAL-SkimlinksPromo%