Anaheim (a.k.a. New Mexico) chile peppers growing in my south sideyard, supported by a small tomato cage.
Staking and Fertilizing
Unless your crops are low growing (e.g., root vegetables, or leaf vegetables like lettuce) or naturally sturdy (e.g., corn, okra) you'll need to provide vertical support for them as they mature. Commercially available tomato cages will support tomatoes, peppers, and eggplants. You can also use stakes and trellises. Holding plants upright prevents fruit from coming into contact with the ground and rotting. It also keeps stems and branches from breaking in strong winds. Tomato cages should be reinforced with t-posts, as the plants can topple over from the weight of their fruit. Cucumbers and squash benefit from trellises. Pole beans, as the name implies, will climb poles.
If you have mulched the soil sufficiently, you might not need to water your crops every day. Gardening manuals advise less frequent, deep watering versus more frequent but shallow watering. Test the soil beneath the mulch with your finger daily. If the soil surface is slightly moist, then your plants have adequate water. Plants will require more frequent watering in hot weather.
Keep the crops fertilized during the growing stage. Slow release fertilizers, be they chemical pellets or organic matter like bone meal, are worked into the soil at planting time, and maybe added once or twice more later in the season. Quick release fertilizers (e.g., Miracle Gro mixed with water) need to be applied more frequently, say, every ten days. Research the particular nutritional needs of your various plants and fertilize accordingly. Beware of adding too much nitrogen to the soil, as excess nitrogen promotes leaf growth at the expense of fruiting.
If your plants begin to wilt or change color, this could be the sign of a nutrient deficiency:
Plant Nutrient Deficiencies
Here is a good general site on vegetable fertilizing:
Garden Fertilizers, pH and Micro-Nutrients
Treat any nutrient deficiencies promptly.
Earlier I mentioned compost (deliberately biodegraded organic matter) as a component of good, rich soil. Here is a good article on the subject:
Compost Guide - Composting Fundamentals
Some plants need to be pruned for maximum crop yield. This means removal of unnecessary leaves and branches so the plant's energy can go into fruit development. With peppers and eggplants, wait until the plant develops two main branches, forming a V shape. Remove all leaves below this V. Tomatoes are divided into two basic types, only one of which requires pruning. Indeterminate tomatoes, which produce fruit continuously from maturity until the arrival of frost season, develop suckers which should be removed. Determinate tomatoes (a.k.a. bush tomatoes), which produce their fruit all at once and then cease production, should not be pruned.
Use a sharp bypass pruner to remove unwanted growth. Between cuts, dip the blades in a disinfecting solution and rinse them with water. This will keep diseases from being transmitted from one plant to another.
Disease and Pest Control
Keep a close eye on your plants for any damage or discoloration. As with nutrient deficiencies, identify diseases or insect infestation according to the symptoms, then act immediately. A single tomato horn worm (the larva of the sphinx moth) can devour most of a tomato or pepper plant within 24 hours. Sometimes it is necessary to pull out and destroy entire sick or infested plants to save the healthy ones.
Some plant diseases (e.g., powdery mildew) can be treated with chemicals like Daconil. Insects can be kept down by regular applications of pesticide. There are also organic pest control methods.
Here is a web site to help you identify plant diseases:
Vegetable MD Online
And here is a site for identifying and controlling insect pests:
Plant Pest Identification
Insects are not the only pests. Depending on where you live, rodents, birds, and deer can also damage or devour your crops. The larger critters can be kept at bay by garden fences, or by enclosures built with chicken wire or hardware cloth (galvanized wire mesh).