1. It's a really good idea to re-check the placement of the outlets, lights, and switches that you decided on in the electrical rough-in stage - it may save you from cutting new holes in the drywall to move these around when you realize the location is less than ideal. Or not high enough to hang the mirrors above the bathroom vanity as a random example (vanity lights were originally pointed down, but they had to be reversed to fit above the mirror).
2. Ditto on the rough plumbing - recheck prior to drywall to ensure the plumbing is located correctly to fit into your cabinetry and vanities. The clawfoot is ever so slightly off center in the window - but had to be to align correctly with the plumbing fixtures installed in the already tiled floor.
4. Select your appliances as early as possible in the process and measure, measure, measure. Don't assume that the latest and greatest models of washers and dryers, for example, have similar dimensions to older models. We ultimately had to stack the washer and dryer because the front loading steam versions I really wanted did not fit as planned in the laundry room.
5. Think carefully and creatively about room layout, considering things like activity and noise levels, light seepage from other rooms, and likely bedtimes of residents and guests. Although we love having the repurposed stained glass window in the main upstairs bathroom, for example, we failed to consider that the room on the other side of the window is the master bedroom sitting room. Anytime someone uses the main bathroom in the middle of the night, the light shines through the stained glass window and right into our bedroom!
7. One actually can have too many wineglasses - hard to believe, but true (and a function of my thrifting AND attending a lot of wine tastings...). I'm in the process of paring down - they just don't all fit.
8. Purge before you pay to store things, not after. Avoid this, if possible.
10. You can save time or money but not usually both (as evidenced by a number of unfinished projects that still remain like the DIY mantel restorations).
11. Spray foam insulation is worth every penny of the additional cost - do it if you can. It pays for itself the first winter, and you cannot beat the snug, airtight comfort.