Once you have identified a problem, you'll need to decide on a course of action. First, remember that some problems are minor or fleeting enough to be ignored: you probably can live with a chewed leaf or two, and some insect infestations may persist for only a week or so, then resolve by themselves as the pests mature or move on. Other problems, however, will be serious enough to require controls. When this happens, don't immediately turn to pesticides. Other, less toxic options may work perfectly well.
Note: If a particular plant looks sickly no matter what you do, the best course may be to abandon rescue attempts. Dig it up and replace it with something else.
These are all simple, time-honored tactics; you remove pests by mechanical means. Check the discussions of individual pests, diseases, and weeds for more ideas.
Hard blasts of water from the hose knock many pests (aphids and spider mites, for example) from their perches.
Handpicking is a straightforward way to get rid of pests such as hornworms and snails.
Sticky traps--paper or cardboard covered with a sticky material like castor oil, natural gum resin, or vegetable wax--are useful. Place 6- by 6-inch sheets on sticks in a vegetable bed to attract flying insects. You can also wrap a stiff paper band (at least 3 inches wide) covered with sticky material around a tree trunk and leave it in place for a few weeks; it will keep insects from crawling up into the branches.
Barriers work well against many pests. Thwart crawling marauders such as snails and slugs by encircling planting beds with a 4- to 5-inch-wide ring of sawdust or a 4-inch-high "fence" of copper strips. A below-ground chicken-wire lining in a vegetable or other garden bed will discourage gophers; wire frames on top of planting beds keep pests such as rabbits, opossums, raccoons, and skunks out. Floating row covers keep insects and birds off some ground crops; netting prevents birds from snacking on ripening fruits and vegetables.