Look in a bird field guide to find out which owls live in your area and where to look for them. A librarian can help you. Also check out online guides and listen to recorded owl calls:
In the evening, listen for owls hooting, tooting, whistling, or trilling. Late winter and early spring are usually the best times to hear owls calling for mates.
Imitate the call of an owl and see if the bird calls back to you.
Return during the day to places where you heard owls calling. Look for whitewash, owl pellets, and owl feathers. If you find some, check carefully up in the trees. There might be an owl tucked next to the trunk or perched on a limb.
Keep track of trees in the area that have stick nests in them. Go back to those trees in late spring to see if an owl mom is using any of them. Take binoculars so you don't have to get so close that you disturb her.
Keep owl-prowling notes in a field journal. Sketch a map of any owl hot spot you find and keep track of what you discover there over time. Use your field notes again next year to see if owls start a new family in the same area.