May is a good time to plant out lettuce either small plants which are sold in the garden centres, or sow from seed directly where you want the lettuce to grow.
sow in a straight line so that when they germinate you can tell seeds from weeds, and thin out to prevent overcrowding. Pick the strongest seedlings and weed out the rest. Frost protection is needed, and a cloche is helpful to get the plants off to a good start. Water well because if the seedlings germinate and then are too dry, they will wither and die.
Beat the slugs
But, soon as the lettuce are there so are the slugs, nothing they like better than a dish of tender new lettuce and then can shred a row of lettuce overnight. Protect the new plants by any one of the favourite methods, organic pellets, grit, or beer traps. For more information on how to beat the slugs follow the link