Squash comes in two main varieties. Summer squashes, which include zucchini, have tender skin and flesh, and are best used soon after purchase. The winter squashes, such as Hubbard and pumpkin, have thicker skin and denser flesh, making them better-suited for longer storage. Properly cleaning the squash gets grit and grime off the rind without damaging the squash, or compromising its storage life if you aren't using it immediately.
Wash the outer rind with warm, soapy water if you aren't using the winter squash immediately. Mix 1 part bleach with 9 parts water and wipe the outside of the squash with the solution. The bleach is dilute enough not to pose a health hazard, but helps prevent bacteria and fungal growth during storage.
Wash the squash rind more thoroughly right before use. Rinse it in cool water and scrub the rind gently with a vegetable brush to remove any soil.
Cut the squash in half with a large chef's knife. Scoop out the seeds and pulp from the center of the squash and discard them before cooking.
Brush any soil or dirt from the summer squash with a dry cloth if you aren't preparing the squash immediately. Brush gently so you don't break the tender skin.
Rinse the entire squash in cool, running water right before you use it. Rub any dirt spots from the skin with your thumb or with a damp cloth. Do not use a vegetable brush to clean tender summer squashes.
Slice the stem and blossom end off the squash and discard them. Slit the squash open lengthwise and scoop out the seeds, if you wish. Summer squash usually has small, tender seeds that don't have to be removed.