I'll tell you what I do, I'm sure you'll get other versions. If I believe the color will bleed, I wash it separately. Otherwise I wash like colors together with regular detergent, and usually on gentle just so cut edges don't fray too much. I never use fabric softener until my project is complete as sometimes this will not permit you do do certain things like some fusible applications won't stick well if you have used fabric softener.
When washing yardage, open your fabric up, don't throw it in your machine the way it came off the bolt as one time I got a color difference on the crease line, although I think it was the quality of this particular fabric.
A mesh bag is great when you are washing fat quarters, as when you are washing a number of them they tend to tangle together, and fray too much.
No reason you can't add other laundry to your load to make a full load, I've done that before! (Usually I'm just to axious to get it washed and start sewing!!)