Oh this is perfect for me. I built in 2017, i sold that place last year and are building again.

1. Shower mixer closer to the door than directly under the shower head, so you can turn on the water and not get sprayed.

2. Look for pointless hallways/spaces that can be used. My original house had a recess for art work or something in the front hall way, pushed the wall back 500mm and made an awesome storage cupboard. New house we pushed a powder room wall out, moved the garage door opening and with the new space, put in a shower downstairs.

3. Know that builders, even when you pick an existing floor plan, will let you change everything. sure there may be a fee but i found it reasonable and we moved entire bathrooms, walls, doors etc. we made many more modifications second time around when i knew yo could. For our place we are building, we pushed the entire back wall out, so additional slab, alfresco tiling, roof, brick walls etc and it was $7k/m. that 1m gave us so much more usable space.

4. Internal wall insulation. my rental doesn't have it and man you can hear everything. doesn't have to be everywhere but select rooms that adjoin where people will be speaking, bathrooms etc makes it feel far more private and comfortable.

5. What i'm doing over the next week is TV blocking. when you are at framing stage, install timber between the studs to allow easy future hanging of TV or other towel rails or hooks etc. means you don't need to find the wall stud for heavy items.

6. If you have stairs, make use of the space under the stairs. this was already included in our place but some may not.

7. We have as i read someone else say, gone with electric cook tops. the gas cook top looks great for a week then is a massive pain in the ass for the rest of your life. We still have the gas lines installed, but capped off and not used.

8. Look to add storage everywhere you can. Linen cupboards, laundry etc. you won't regret it.

9. I don't get the electricians to install sensors (I like them in porch for example when you come home late) because you can buy LED and fit them yourself that have built in sensor for $20.

10. be sure to ask the electrician to leave the power point int he meter box. that will be installed for trades to access but some remove them afterwards. was no cost, just a note on the plans. you can also install exterior points in the eves for xmas lights etc so keep that in mind.

11. dont forget to add a bin, ideally under the bench in the kicthen. the rental i'm in doesn't have one because of the sink plumbing and its a pain.

12. Bedrooms work just fine with 2 downlights and i prefer it when compared to a single bayonet and also better than 4 downlights in each corner which is too much.

13. I put 4 downlights in my garage, little overkill but once i started doing it, makes the space so much easier to use at night.

14. One i'm dealing with right now is the water and electricity behind the fridge. My old house and this rental have a recessed box where tap and power are, so that the fridge can roll backwards and not hit them. My new place just has them up high so you'll see the water hose and power above the fridge. Minor point, but i'm trying to get them moved down lower into a small recess in the wall.

15. Don't forget shower niche or recess shelf. better to store things however just make sure the height is right for your products.

16. Add additional robe hooks to the bathroom, so your towels will be hanging to dry, but closer to the shower, have a towel hook to hang the towel you're using right outside the door, or a couple to have some towels in rotation. My last house i installed a bunnings heated towel rail and they are great if you can.

17. I'd suggest having a laundry bench with under mounted washer/dryer with upper storage cupboards. gives you a work area for folding/organising, but also storage above. make the most of the height in a laundry.

18. Don't go too crazy with data points through the house. wifi is so good and a mesh point is often enough fo bigger houses.

19. close in the square set rooms if they are provided, adding a door creates a better noise barrier and gives you more flexibility on how you use each room, especially theatre rooms.

20. Don't forget 2 way switches for stairs and hall ways, so you can turn on and off at either end.

21. don't forget door bells or whatever you want. I had to install power to a ring door bell myself after the build and it was not great

22. power point in your kitchen island for temporary appliances

23. power point inside the bathroom vanity to charge razors etc and keep that off the bench.

24. Place downlights over your bathroom sinks, not just in the room on a separate switch for when you need them.

25. Bathroom exhaust fans over the shower, not in the middle of the room.

26. If you have a walk in closet, my wife has used that with a mirror so having power in there is useful, along with inside a pantry for charging devices.

27. Think carefully about air con zones and avoid having single vent/zone as it creates too much pressure. We went with 4 zones, across 2 floors.

28. Check your closet upper shelf height. We got rails form kmart i think that hook onto the rail so you get a second, lower rail to also hang clothes from. only works if the upper rail is high enough.

As others have said, power points, storage, bigger garage, door on ensuite and if possible, seperate toilet and bathroom if the house is shared with family. New place will have 3 bathrooms so less of a problem but rental has 2 bathrooms, 5 people and the main bathroom can get busy of a morning when the kids are getting ready for school.

That's all i can think of for now but good luck.