I don't care for the "if it's yellow, let it mellow" rule. That's too gross for me - but at the rate I'm collecting waste water, it's not an issue.
Since we started this a few months ago, we've cut our water usage in half. I am convinced we can cut even more.
Collecting warm-up water from the sink. Think about how you wash dishes when you camp - scrape the plates first, use a dishpan with soapy water, rinse all at once, dry in a rack. Add warm-up water and soapy water to bucket for flushing.
Collecting washing machine rinse water Stopper the wash tub, use a bucket to bail into tall trash cans and plastic storage bin. The only trick is to not overflow. I'm still experimenting with various solutions. (I wish one tub would overflow into the other, but they are level. I've tried a diverter, but it still needs work.) My current solution is to watch a movie or work downstairs while doing laundry and listening for it so I can bail as it drains.
The Home Depot bucket and smaller bucket used for flushing by pouring directly into the bowl until it flushes. Usually hidden behind closed curtain. I carry the orange bucket form the basement once or twice per day.
Surprise gray water bonuses
Gray water smells nice like laundry soap - it's free air freshener!
Needing to refill the buckets is an incentive for staying caught up with laundry!
Going into the laundry room regularly keeps cat box maintenance on schedule!
Stair climbing and weight training without the expense of a gym membership!
Not only reuse waste water, but uses much less water to flush!
Pride at one's thrifty-greeness quickly overshadows minimal grossness factor!
For the future:
Explore actually replumbing the house to use gray water.
Keep an eye out for more attractive, less obtrusive buckets