Grow salad plants
On a poor site, especially one that tends towards being sandy or dry, you're unlikely to get a good crop.
Even with a good site it's worth adding well-rotted manure or garden compost to add nutrients and increase the soil's ability to retain moisture.
A sunny or partially shaded site, with soil that is moisture-retentive and rich in organic matter, offers the best conditions for summer salad crops.
Don't restrict lettuces to the vegetable plot. Lettuces with frilly, ornately shaped or beautifully coloured leaves can be grown ornamentally in other parts of the garden. Use them as border edging or simply dotted in among other plants.