Here are my tips for growing great lettuce:

Site, soil type:

The soil should be of medium fertility.   Plant in fine soil that has had organic matter applied.

Shade will prolong the time before lettuce bolts (flowers) and turns bitter.

Planting requirements:

Plant when soil is as low as 40 degrees.   Lettuce is frost tolerant, although not as tolerant as spinach or kale.

Plant seeds very near the surface covering the seeds very lightly.  They need light to germinate.

Thin to four inches apart and grow until they are a few inches tall.  Then thin these small plants and use for early salads.  Eventually plants should be 12-16 inches apart.

Nutrition/Fertilizer needs:

Add one cup of organic fertilizer per 10 feet of row.     Water every week or two with fish fertilizer for a quick boost of nitrogen.

Water needs:

Keep moist at all times for optimal growth.

Other tips:

Summer lettuce may turn bitter.     Varieties I’ve found that don’t get bitter until later in the summer are Nevada, Cherokee, Winter Density and Sierra.

Rinsing lettuce under warm water may help reduce bitterness.

For quick growth in the cool spring, nothing beats the variety Black Seeded Simpson.  Winter Density is very hardy.

For nutrition (carotenoids, vitamin C and folate) romaine lettuce is the winner over the other types (leaf, butter, and crisp).