Human and flaws
Someone that has never played chess before, once the rules have been explained, will usually play fairly randomly. You can't expect much more from lazy humans... unless you place a lot of money on a win (or threaten to push them off a cliff if they loose). In this case, the approach they will attempt to take will be very naive: they will attempt to think through most options, trying to plan ahead a couple moves. They will not do very well at this, since they'll miss out some key moves, and tend to forget what the context of their train of thougt was.
Humans are bad at this. But they have the benefit of pattern recognition and learning to give them the edge... cue the grand champions.