Research about clutch hitting usually turns up little evidence that the ability to raise one's game based on the situation is a skill players possess. First of all, clutch is difficult to define. By the time you throw out many of the situations fail to qualify, a researcher is left with a small sample, and in a small sample almost anything can happen.
The other thing you notice is that list of the best hitters in a particular situation tend to match the list of the best hitters in any situation. This list of the players with the best batting average with runners in scoring position over the last three seasons (2008-2010) contains a number of the best hitters in the game. One name near the top did catch my attention, however, David DeJesus.
David was one of the better hitters on the Royals during this time, but as a leadoff man we don't think of him as a clutch performer. His job is to get on base for the big bats, after all, yet his batting stats change as the situation is more likely to yield an RBI. With none on, he posted a .283/.351/.433 slash line in that time. With men on, .328/.383/.459. Finally, with men in scoring position, his line comes in at .340/.398/.458. Note what's happening here. His batting average goes up more than his OBP, and also more than his slugging percentage. He's replacing both walks and extra base hits with singles. Looking at his line drive rates in these situations explains why that is happening:
Finally, David's percentage with runners in scoring position come in at 48% ground balls, 22% fly balls, and 25% line drives. His focus seems to shift from hitting the ball in air to hitting the ball through the infield, and he really hits the ball on the nose in the strike zone with an RBI a single away.
Of course, this could still be just a bit of luck. We're looking at 275 balls in play with runners in scoring position, so luck still plays an enormous role. Still, if I were to suggest a strategy that resulted in better clutch performance, reducing fly balls and trying for more line drives (especially for a low power hitter) would be the way to go. It helped DeJesus drive in a very high percentage of the runners he finds on base over the last three years.