At campgrounds, properly store food day and night. Bears may enter campsites during the day, even if people are there. Keep a clean camp. When day hiking, properly store all food and related supplies in bearproof food lockers where available at trailheads. Don't walk off and leave your backpack.
Bears recognize packs as sources of food.
A Word of Warning Do not underestimate a bear's ingenuity, strength, or reach. Should a black bear approach, act aggressively toward it. If the bear continues to advance, retreat. Never approach a mother with cubs. She will attack in defense of her young.