If you prefer to raise transplants, they should really be started two or three weeks earlier than I have listed. Transplanting, no matter how carefully done, shocks the plant. It is sometimes advantageous to raise transplants, though, either because your garden space is limited, or because you find it easier to manage the environment needed to assure good germination. In the Maritime Pacific Northwest, many otherwise-hardy plants will not survive over the winter. Because our consistently damp winter weather provides a haven for molds and fungi.
Leafy greens are especially succeptible.
Raised beds, combined when possible with cloches or a PVC hoophouse. Raised beds can be elaborate affairs, framed with wood or plastic lumber specially manufactured for this purpose. As long as you never step on the beds, and don't leave them bare through the winter, you probably won't have to remake them for many years. Cloches are essentially plastic tents for your plants. They can be easily built from all sorts of materials.