Tips & Techniques for Growing Lettuce
Varieties of Lettuce
Lettuce is a cool weather plant which does best early before the weather turns hot.  The two main types are looseleaf and head lettuce.  There are many varieties of looseleaf lettuce.  Some are light green in color while others are dark including red and purple.  Lettuce leaves can be smooth or frilled.  Likewise, head lettuce can produce round or long heads with varying textures.  When selecting varieties to plant, you may want to look for some that are slow bolting and tolerant to heat.  When lettuce bolts, it sends up a stalk and starts producing flowers.  Energy is diverted from growing lettuce leaves to making seed.  Black Seeded Simpson is a good looseleaf variety with tender light green leaves.  Buttercrunch is a popular head lettuce.
Preparing the Soil
Since lettuce seed are so small, the soil needs to be very loose when planting lettuce.  If you do not have sandy soil, you may want to till in some compost to prevent the ground from getting too hard.  Unless you are planning to save seed, pollination is not a concern, so you can plant just one row or several.  Preparing the soil is as easy as tilling and marking off rows.  Using a hoe, make a straight shallow trench.  The seed can then be sowed in the trench.  Unlike most garden plants, lettuce does well in the shade.  You may want to select a location next to taller plants, e.g. pole beans, that will provide some shade. 
Planting Lettuce
Lettuce should be one of the first vegetables planted. It can handle a light frost.  Lettuce can be grown in beds or rows.  I prefer planting it in rows.  It is easier to weed and pick.  Sow the seeds in a shallow trench and cover them with approximately a quarter of an inch of dirt.  If you plant them too deep, they will not be able to push up through the ground.  Be careful not to sow the seed too thick.  You want a good stand but not so many plants that they will not produce nice size plants.  If you plant it too thick, you can pull up some plants as you gather lettuce to eat.  Planting several varieties of leaf lettuce will provide variety to your salads.  Several varieties can be planted in the same row but head lettuce usually takes longer to produce.
Weeding & Plant Maintenance
If you plant your lettuce in rows and made the middles slightly wider than your tiller, you should be able to remove the weeds from the middles with a single pass of your tiller.  Since lettuce plants will be close together you will have to pull most of the weeds that are in the rows.  You should till and hoe about three or four times during the growing season.  If water is available, you may want to water, if it doesn’t rain for a week or two.   Lettuce will grow fast, if it gets adequate moisture. 
Controlling Diseases and Insects
Lettuce can be attacked by several diseases, with the most common being downey mildew and bottom rot.  Some common pests are cabbage worms, aphids, and armyworms.  However, I have been able to grow lettuce without very much of a problem with them.  My biggest problem has been with wildlife.  It seems a lot of critters love the tender lettuce leaves including deer, rabbits and groundhogs.  To detour them, I have sometimes used an electronic owl that detects motion and makes owl sounds.  It works for several weeks but eventually they become accustomed to it.  I have resorted to putting part of my garden within a fence and lettuce is one of the vegetables I place in the fenced area.  If you find that a fungicide or insecticide is needed, make sure you pick one for the specific problem and that can be used on garden vegetables.  You need to be especially careful when applying chemicals to edible plants like lettuce.  Always read and follow the directions on the containers. For specific details on controlling diseases and pests, click on the "Gardening Resources" tab and go to the Sources of Information on Vegetable Garden Diseases and Pests.
Leaf lettuce can be picked and eaten as soon as the leaves are large enough.  If you break off selected leaves or cut the leaves off about two inches above the ground, the base of the plants should generate new leaves and continue to produce lettuce.  Of course, you will need to wait to pick head lettuce until the heads are of adequate size.  Lettuce is best eaten fresh and does not keep long outside of the refrigerator.  Various types of lettuce and other greens can be mixed to make salads more tasty and colorful.