Don’t use too much soap! Most people use way more soap than needed leaving residue in clothing and lowering the efficiency of the washing machine.
Don’t overstuff the machine. Wash full loads but you don’t want to fill so much that your clothes wont get clean. A good rule of thumb is about 3/4 of the way to the top of the drum.
Pre-sort your loads. Pre-sorting before leaving the house saves you precious time.
Do your laundry at an off time. Doing your laundry at a time when the laundromat is less busy will allow you to get more loads done at a time saving you time in the end. Neighborhood Laundromats are open 24/7 so anytime can fit your busy schedule.