You'll need a few lemons for models and some salt (any kind will do). I used 6 different pigments -- Aureolin Yellow, New Gamboge, Quinacridone Gold, Raw Sienna, Quinacridone Burnt Orange, and Quinacridone Magenta.
Now, prep two colors on your palette, to use for the first wash -- Aureolin Yellow (cool yellow) and New Gamboge (warm). And, have some salt handy. Wet each lemon separately, and then paint
these two yellows onto each lemon. Allow some of the yellow to move into the shadow. When there is just a sheen on your paper, sprinkle on some salt. Do this for each lemon, and let this dry completely
Now, mix a dark, using the Quin Burnt Orange and the Quin Magenta. Use this mixture to add a few darks to the stem area of the middle lemon and to the part of the cast shadows, directly below the lemons. Paint it onto dry paper, and then soften the edge with a damp brush.