Surf (takes out sweaty smells from hubby’s work clothes) with colorsafe bleach. Regular bleach on the whites. Downy if I’m feeling energetic.
Most stains will come out with water and time. For protein stains, like blood, you must use cold water. Hot water will set the stain. Warm/hot water is okay for oily or greasy stains. When in doubt, though, stick to cold.
When something is stuck to a piece of cloth, like candle wax on a tablecloth or gum on a kid’s shirt, put the cloth in the freezer overnight. Then you can scrape the mess off with a dull knife, and proceed from there.
If you overload the washer, the clothes will not get clean. The dirtier the clothes, the more space you need to leave in the washer.
I use a powdered “micro” detergent, about half the amount specified, and concentrated fabric softener. Cottons get washed at 60C, and I rarely have problems with stains, even with two small boys in the house. Synthetics at 40C, woolens at 30C. (I’d like to thank the genius who invented wool wash cycles for front-loaders!) The baby’s diapers get a prewash with an enzyme detergent, then a regular wash at 60C, and no fabric softener.
And in case anyone’s interested in Norwegian cleaning products: Blenda Sensitive for whites and light colors, Blenda Color for darks and brights, Biotex enzyme detergent for prewashes, and Comfort Sensitive fabric softener.
My mom. 
One of perks of living at home while you go to school.
Seriously though. When living on my own all I used was straight laundry detergent. No fancy sheets or liquids (mostly because I was poor and I figured that detergent alone worked well enough). The secret was to run the clothes through the machine twice, once with detergent and once without, then air dry.
As for getting blood out I highly recommend Hydrogen Peroxide. Works like a charm. It saved me from several wrecked shirts.
Can we talk about Dryel? That’s the thing where you put your dry-clean only clothes and a special sheet in a bag in the dryer for 30 minutes. I personally love the stuff and have addicted my mother, sister and several friends to it.
It doesn’t work for really sour smelling clothes, but I LOVE it for my everyday stuff.