Morels appear throughout the continent in spring. Trees are just beginning to bud, so relatively unfiltered sunlight warms the earth directly. This triggers the appearance of a number of wildflowers: trillium, phlox, trout lily, Dutchmen's breeches, violets, wild strawberries and many more. Along with the temperatures, these flowers are indicators of when to look for morels.
The "where" isn't quite as simple. Where the spores fall, cross-pollinate and germinate is where morels will grow-after a five-year cycle of nutrient-gathering and storage. Black morels (which appear first) tend to be more exclusively in hardwood forests, but not around any particular type of tree. Finding them is often like a connect-the-dots game. When you find one, be still, and look nearby. When the spores that created the morel you just picked were jettisoned years ago, there likely was a wind pattern that blew the spores in a particular path. There may have been a nutrient source or environment (soil type, moisture, pH, etc.) that was conducive for growth. Look for the patterns.
Mother Earth News: Morel Mushrooms. randomWalks says don't eat unidentified mushrooms.
