In the spirit of Nathans post, I had him make me my very own flag:
Our house water filter needs to be replaced. I found this out because the washing machine intake filters (just some wire mesh placed at the end of the hot and cold water feeds) filled up with tiny pebbles. I yanked the washing machine out of its niche, unattached all the hoses, cleaned out the filters, reattached the intake hoses, and turned the washing machine back on. Those of you who have done this before may notice one operation that's missing from that set.
I started a load of laundry, and when I went into the kitchen for something, I found out what I had forgotten to do. Yep, I forgot to put the exhaust water hose back in the drain pipe.
Fortunately, I discovered this before the rinse cycle dumped a second load of water on the floor.