When planting lettuce you can buy seedlings, or sow seed. Seed gives a greater variety to choose from and also eliminates the shock of transplanting. Also, you can enjoy the rewards a lot earlier by starting your seeds off indoors, in a greenhouse, cold frame or under cloches and enjoy your crop for an extended period by the use of these mediums. If you use a cold frame, it will not only protect your early or late plantings but, by the use of the appropriate shade cloth, can offer summer protection too.
For direct planting of lettuce seed into a well-prepared bed, rake the soil continuously until you get a very fine tilth which allows proper contact between seed and soil. Use string attached to a couple of stakes, if you are sowing in rows, to give you a straight line, to make a 1/2in furrow for the seed to go in. Then gently cover the seeds with soil and water gently but thoroughly.
Rows should be 12-15 inches apart to suit the variety of lettuce you are planting, read the instructions on the back of the packet. You can make the rows wider, so you can plan successive sowings in between, as a rule of thumb 18 inches for leaf and 24 inches for other types. You need to thin the seedlings out to allow normal growth.
The plants will require plenty of water as they have a shallow root system and to help retain moisture, use organic mulch which will also keep the soil cool and deter weeds. For a longer season make sure you are continuously planting lettuce, say every two weeks.
Moving on to harvest time make sure you pick them when they are young and tender as they tend to get bitter if left too long. With the leaf variety, just remove the outer leaves and let them continue production. Butterhead or romaine types can also be harvested this way, or just removed from the soil completely.