Summarize the following:
Loose leaf cultivars are the brightly colored, nutritious lettuces often sold in a "spring mix." These lettuces tolerate warmer temperatures and a shorter growing season than other varieties, so they are usually scattered directly in the garden.  Head lettuce should generally be planted indoors instead. Hot weather triggers "bolting" in lettuce, halting leaf growth and introducing a bitter flavor. In hot climates, such as the southern U.S., you'll need to plant the lettuce as soon as possible, or look for a heat-resistant variety. You should plan to plant the lettuce as soon as the ground is workable. Choose an area with soil that drains well and gets plenty of sun. Use a soil tiller or a spade to break up the soil and remove rocks, sticks and roots from the area.  Lettuce is hardy, but there are certain conditions that won't allow it to grow properly. Make sure the soil isn't too soggy, and that it has plenty of nitrogen. Make sure the soil is humus rich as well. Talk to someone at your local nursery to discuss ways to enrich the soil in your particular region to make it excellent for growing lettuce. Mix in compost or a balanced fertilizer into the bed at least one week before planting. Optionally, you can apply a nitrogen-heavy fertilizer alongside the plants after about three weeks, when leaves are four inches (10 cm) wide. Lettuce is cold-hardy, so you can usually plant them directly in soil about two weeks before the last expected spring frost, or up to six weeks in advance if protected by cold frames or tunnels. Broadcast the seeds over tilled soil, then scatter about 1⁄2 inch (1.3 cm) of soil on top of them. One seed packet will cover about 100 feet (30.5 m). Water the seed bed thoroughly after planting. Stagger the planting at one or two week intervals to get harvests throughout the season. Keep in mind that most lettuces do not grow well in hot temperature, so the last planting date depends on your local climate and the needs of your lettuce cultivar. For best results, use heat-resistant varieties or plant in shade for the final sowings. If the leaves look wilted, they need to be watered. Give the lettuce a light sprinkling every day, and any time the leaves look a little limp. When harvesting looseleaf lettuces, use scissors or a knife to remove the mature leaves without harming the rest of the plant. You can start doing this as soon as the leaves reach the size you'd see in a grocery store. Remove the whole plant after a few weeks, or the plant will turn bitter and start to seed.  Harvest in the early morning for the crispest leaves. Pinching off the center of the plant will extend the harvest period. Store lettuce leaves in the fridge for up to ten days, keeping them in a plastic bag with a couple paper towels.

Summary:
Choose a loose leaf variety for outdoor planting. Prepare the planting bed. Fertilize the bed. Broadcast the seeds. Keep the lettuce watered. Cut away mature leaves.