With a shoe laundry bag, you can have your sneakers washed in the washing machine and they come out clean!
For jeans, have them turned inside out before you throw them in the washer so that the color lasts longer, too.
As for the detergent amount, use less than what is recommended (unless your clothes are really soiled).
Hang dry your clothes and avoid using the dryer. It takes about 15 minutes or less to hang clothes (for those who are really bored, listening to music makes the task go by faster).