You are going to need some plants or seeds.
In the spring, your local gardening supply center should have a variety of lettuce seeds, plants and other greens available for planting after the last frost.
Or, you can search the web to find your plants or seeds. During late fall and winter is when most seed catalogs are published and, if requested, will arrive in the mail. Much can be learned from reading these catalogs, allowing you to garden in your mind during a period when it’s not possible to do so outside in your real garden. A good garden usually has had some thought and planning involved, as well as the physical things like digging and planting.
Try not to get carried away with those visions, though, and keep it practical and doable. Keep in mind how big your plot is and how much sun it gets, as well as your own physical abilities. Digging good beds can be hard work, though once you have cleared out rocks and roots and built up the soil with compost etc., it should be much easier to prepare in following seasons.
I like a variety of lettuces and herbs, plus other greens and veggies, growing through the season to keep my dishes and salads interesting. Also, some lettuces and greens may grow better during spring, summer or fall. When some plants have finished being productive, you will have to pull them and prepare that space for the next planting. Not too hard really, but it can be hard to decide it needs to be done when a plant has given so much. On the other hand, some plants just won’t make it, and you will have to give up and try another in its place. This will be especially true if you have limited good growing space as most backyard gardeners do.
In my case, I usually grow loose leaf lettuces which can tolerate individual leaves being picked as needed. Some plants can yield for 2 or 3 months before they will go to seed. You may find that there are a lot more kinds of lettuces than you have ever tasted, which means that there could be some nice new flavors to try.