What to consider...

 This is going to be a long one! I'm sure as time goes on, I'll reorganise it, but for now, I'm keeping it simple!

• What heating system are you going with (or are you going passive, so none needed)?
• Yeah, so everyone thinks about this, but no one thinks about the location of the various elements of the system chosen. If you go with Under Floor Heating, where are the manifolds going? You need to have a central place to locate the pipe manifolds (think of a row of pipes sticking out of the ground with knobs on top) .. you'll need to be able to access it easily, but who wants to have this in the way or visible? So account for it, have a spot picked for the manifolds where they can be 'hidden'.
• Where will the ironing board/mops/hoover go?
• Particularly where will the wall mounted cordless vacuum go? They protrude from the wall, so make sure there's a nook for it with a socket nearby.
• Task lighting and ambient lighting
• You may or may not want both everywhere, but get a lighting design done by a professional! It is invaluable! 
• Get started on your kitchen design as soon as you think about house designing... 
• Not necessarily the finishes, but the layout and positioning of appliances, sockets, isolation switches...
• Where will the bedlinen and towels be stored? No such thing as hot presses anymore!
• Where will the heating system, ventilation system, and water system units be located? 
• You do not want any of these these near a bedroom!
• Build a plant room! Trust me!
• Make sure the electrician wires the house with FIBRE-level cabling. Most of them still use copper internally, which won't work for fibre to the home broadband - spec it and make sure the electrician follows it.
• Have an electrical plan designed EARLY - alongside lighting plan.
• Be prepared to ask 'why' every time you're told no/not possible. Just because it's harder to do doesn't mean it's impossible - it is YOUR decision and YOUR money, so it's also YOUR call!
• Budget for landscaping as part of the build. 
• Having the topsoil spread and ready to seed/plant as early as is practicable with regard to the build progress, it might be at the very end of the build, but grass seed grows quick and green is so much nicer than mounds of brown to look at!
• Plant trees, shrubs, hedging as soon as you can, don't wait till after you move in - when the build works will no longer impact their locations. They get time to mature and you are being productive when there's less for you to do.
• Once the build nears the end, you will be so busy, so anything you can do before that, DO IT! 
• Mood board out your rooms, and be willing to change them as the build evolves
• Time is money. 
• Just because you can do something yourself doesn't always mean it's the right thing to do. If it's money you have and can afford, get someone else to do the work for you. Compromise on the things you can do yourself and delegate others. Your time is as valuable as others. So it might mean getting the house spray painted rather than painting yourself, but you can then use the time to do something else that's necessary (building furniture, etc etc).
• Sign an RIAI contract with your builder - you can order these (the blue one) from RIAI directly.
• Ask the builder to seek sign off from yourself on any changes/alterations and the pricing before committing to proceeding with them. Have the next stage payment include these additions, rather than waiting till the final stage payment - when it hurts the most!
• DO NOT BUY FURNITURE too soon. 
• Live with the space, use old bits or handmedowns, borrow, you'll be glad you waited as you'll have a different attitude after a period of time in the space. Don't waste money on regretted purchases.
• Trust your gut! If it feels right, it is; if it feels wrong, it is wrong. 
• Be flexible, be willing to go with the flow and change your mind/approach.
• Don't stress about things you cannot control.
• Ask the stupid questions - of all the trades and your builder. Ask the why, to understand!
• Take photos 
• Of the pipework
• Of the electrical cabling
• Plumbing
• Drainage
• You WILL need to refer to them in the near future, trust me!
• Take photos of the build from the same spot periodically, it's amazing to see the progress as it moves along. It's good to reflect on your achievement!
• Identify the priority items for you - be mindful of what is easy change in the future and not so easy change.
• Expect settling cracks and pops. Some will happen, it's ok! If they're excessive, they're not, and don't be afraid to investigate and follow up!
• CHASE people and feel no shame. Be the squeaky wheel. Your money is as good as anyone else's, do not be fobbed off.
• Enjoy it, it's so much fun!

TBC!