If your plants are relatively dense (within 8 to 12 inches of each other) and are aligned in rows you can use a couple of efficient products like drip tape or soaker hoses. Drip tapes attach to a water source and have small holes every 12 inches to water plants. Soaker hoses are porous tubes that allow water to drain directly through the hose into the soil; they will distribute water evenly and you can control the rate of the application.
When planning your garden you should take into consideration the water needs of each plant, the density/spacing of your plants, and ways to reduce the amount of water and equipment needed to sufficiently hydrate your plants. Staff in the Garden In Every School program prefer to use micro-irrigation drip systems. They are easy to install and manage, plus there are a variety of fittings so you can create custom irrigation designs.
You can use micro-irrigation fittings to target specific plants or you can use hoses that apply water evenly to a wider area. Targeted fittings include bubblers (seen below) and shrublers, which can be directed to the base of a plant. These come in handy with low density plantings and they help you meter the amount of water each plant receives. Bubblers generally come in 1 Gallon/hour to 3 Gallons/hour settings, while shrubblers can be adjusted by dialing the fitting head to the needs of plants and can emit up to 5 Gallons/hour.