You pull a shirt out of the dryer and it's two sizes smaller than when it went in. Your kid looks at it, then at you. You have no explanation. This guide is so that doesn't happen again.
Laundry isn't complicated once you know three things: what shrinks, what bleeds, and what never goes in the dryer. Everything else is details.
Wash everything in cold water. Cold is almost always safe. Hot shrinks things and fades colors.
Turn dark clothes inside out before washing. Keeps them from fading.
Don't overload the machine. Clothes need room to move or they don't get clean.
Dry on low or medium heat. High heat is where things go wrong.
When in doubt, air dry. Hanging something up costs nothing and saves the item.
Cotton, wool, and linen shrink in heat. A cotton t-shirt that fits on the way in may not fit on the way out if you dry it on high.
Fix: wash cold, dry low or air dry. Most cotton is fine in the dryer on low. Wool and linen should usually air dry.
New dark clothes, especially reds, navys, and blacks, can bleed dye onto lighter items in the same load. Wash new dark items separately the first time, or with similar colors only.
A color-catching sheet (sold at any grocery store near the detergent) can help if you're mixing.
Wool sweaters, they shrink and felt
Anything with "dry flat" on the label
Bras and delicate items with underwire
Rubber-backed rugs, the backing breaks down
Anything labeled "dry clean only"
Silk
When in doubt: check the tag, or air dry it.
Tub with water: machine wash. Dots inside = temperature (one dot = cold, two = warm, three = hot).
Tub with X through it: do not machine wash. Hand wash or dry clean.
Square with circle inside: tumble dry okay. Dots = heat level.
Square with circle and X: do not tumble dry. Air dry only.
Triangle: bleach instructions. X through it = no bleach.
Iron symbol: can iron. Dots = heat. X = do not iron.
Treat immediately. The longer a stain sits, the harder it is to remove.
Cold water first. Hot water sets protein stains (blood, sweat, food). Cold water first, always.
Don't rub, blot. Rubbing spreads it.
Check before drying. If the stain is still there when it comes out of the wash, treat it again before putting it in the dryer. Heat sets stains permanently.
Never put something in the dryer if the stain didn't come out in the wash. That heat makes it permanent.
Put the kids' socks in a mesh laundry bag before they go in the wash. Every pair goes in together and comes out together. No more hunting for matches at the bottom of the basket or losing one to wherever socks go. A couple of mesh bags costs almost nothing and solves a problem that will otherwise drive you insane forever.
The whole system in one line: cold water, low heat, check the tag when you're not sure.