Peace lilies generally need 4 things to thrive and thus bloom: warmth, light, judicious fertilizer, and lots of water.
They're one of very few potted plants that don't drown if overwatered (though they can still be susceptible to root rot, so if your plant's soil stinks, that may be the problem). Overall though it's hard to overwater a peace lily; that's why they are often used for those cute fishbowl planters.
Warmth and light go a long way, too. Our peace lily blooms wonderfully in the summer and not at all in the winter. The only difference is shorter days, cooler temps, and I don't fertilize in the winter because biologically that's the plant's down time.
When I do fertilize (usually March through October) I do it once a month. You don't want to overfertilize.
I generally use an organic all-purpose fertilizer, but if you're specifically looking for blooms there are fertilizers geared toward that.
Good luck with your peace lily!