Put the dirtiest on bottom. “Dreaded, dried-up messes” on casserole dishes, serving bowls, and pots “need the most intense spray power and heat.” Place them facedown in the bottom drawer. Flat items like cutting boards should be set upright, with the dirty side facing inward, so they won’t block water.
Keep small items on top. Bowls should line the center of the top drawer, with those in the rear facing forward and those in the front facing backward “so the center sprayer can reach them all.” Secure coffee mugs between prongs to keep food and soap from getting caught inside. Plastic storage containers should always be on the top drawer since “they can melt and warp if they get too close to the machine’s steamy underbelly.”
Put utensils in the basket. Position knives tip up, but avoid putting in sharp prep knives as they could dull.
Source: Every Day With Rachael Ray