Harvest Crops at Their Peak
Visit the vegetable garden daily so you can harvest crops at their peak. For example, pick green beans before the seeds bulge the pods; harvest zucchini when it's 6 to 8 inches long. You'll get the tastiest, most tender, and most nutritious food, and you'll encourage the plants to continue producing.
Prune Tomato Suckers
Tomato plants produce abundant suckers -- shoots that arise where a branch meets the main stem. Removing suckers will decrease the overall number of fruits produced, but will ensure that the remaining tomatoes will be larger and will ripen sooner.
Use Fabric to Tie Up Plants
Tear up an old T-shirt or other soft fabric into strips (or use purchased soft plant ties) to bind climbing roses, tomatoes, and vines to their supports. Twine or wire will almost certainly damage plant stems.
Watch for Cabbage Loopers
If the leaves of your cabbage-family plants, including broccoli, cauliflower, and kale, have lots of holes, they're probably infested with cabbage loopers or cabbageworms. Inspect plants carefully for the light green caterpillars, and/or their dark-colored droppings. Use Bt -- a biological control that affects only caterpillars -- to control them. (Note that this insecticide also kills other caterpillars, some of which may be the larvae of butterflies you enjoy, so use it sparingly.)
Water As Necessary
The only way to know if plants need water is to dig in -- poke your finger in the soil or dig near the plant with a trowel. For most plants, you want the entire root system to be moist. Frequent light sprinklings won't do that, and even downpours may not if most of the water runs off.