The first thing to know about planting bulbs is getting the timing right.
When to Plant Spring-Blooming Bulbs
The best time to plant most spring-blooming bulbs (including tulips, daffodils, and hyacinths) is in fall when the soil temperatures have cooled but before the ground freezes. That said, if you're in a pinch, you can plant bulbs on those occasional warm days in January.
When to Plant Summer-Blooming Bulbs
Most summer-blooming bulbs, on the other hand, are best planted in spring, after the soil has warmed and all danger of frost has passed. Hardy lilies are an exception -- you can plant these bulbs in spring or fall.
Most bulbs do best in well-drained soil and are prone to rot if they're in a spot that stays wet or has very heavy clay. In heavy soils, it's often helpful to amend the planting hole with organic matter or even a several-inch-deep layer of sand under the bulb to increase drainage.
More Planting Tips
Water your bulbs in well after you plant them. Then spread a layer of mulch over the soil to disguise your planting holes -- this can discourage critters such as squirrels from digging up your bulbs.