1. upgrade upstairs AC unit to higher seer rating and main level furnace to high efficiency.
2. have framers "screw and glue" floor sheathing to reduce any floor squeeking.
3. get nice wood windows. Personal pref. I hate vinyl windows.
4. if you are going with cheaper interior door options, go with solid core, not too much of an upgrade cost.
5. Buy extra room Toto toilets. They never plug up.
6. If you have attic space that is stick-framed instead of trusses, sheath any space you might be able to use for storage and put in an attic ladder.
7. Pay to put in rebar for your exterior concrete work, especially driveway. I prefer #4@12" both ways...but what do I know.
8. Upgrade your carpet and pad and get a nice nylon fiber or the nicer poly fibers.
9. For cabinets, if you are going with alder, use clear alder, not knotty.
10. use spray foam to seal all window and door cracks prior to drywall.
11. 9' ceilings in basement.
12. Get a real fireplace. Gas fireplaces are like getting to second base and going no further. Hard explaining to kids how santa is going to break through the glass covering.
13. Tile in kitchens....never. use hardwood, much classier.
14. Trim out the interior casement for windows. Looks nicer than drywall.
15. Laundry rooms upstairs are great.
16. More outlets in kitchen island.
17. think hard about where you want outlets placed for convenience.
18. 50-year arch shingles look nicer than 30-year. Look at Tamko Vintage.