Who is the builder? Some are more on the ball than others.
Agree re BT. They couldn't process our order until a certain amount of work had been completed on the development, but they handled it all and kept us informed. We were connected by day 2.
If you aren't arranging flooring through the builder, it's worth asking if you can get access a day early for fitting. Ours were fine with that, although they did mess us around with the move in date. They'll also need to let the fitters in to measure up beforehand.
Our builders left us with two pots of paint and a brush for touch ups along with chocolates and fizz!
Double, triple check that your furniture not only fits in the rooms but can be manoeuvred into the rooms. I inadvertently bought a giant sofa which didn't fit through the hall - had to get joiners to take the window out. 
similarly, check the clearance height on the stairs. Our super King mattress didn't fit and had to be swapped for two zip-link mattresses.
Ask now about their walk round/familiarisation processes. Push for your initial walk round to be as early as possible to give them more time to fix stuff before you actually move in and the repairs become disruptive. We had one two weeks before we got the keys, one the day of moving and another 5 days later to pick up any issues we'd uncovered. It's good to know how they do it as our first one took 3 hours - they show you how to work EVERYTHING.
Don't pay for fencing! You're just paying for your neighbours to get fencing - instead befriend the landscaping contractors on site and do a deal with them. Same with turf if that isn't included.
Order bins from the council early, ours took ages to come.
It'll take ages for your address to appear on maps or sat nav - write out detailed directions and save on your phone/ email so you can easily send them to delivery drivers etc. And yes to getting a house number asap!
Be nice to the site staff! Some of our neighbours learned this the hard way, but we were always pleasant to the site manager and his assistant so they did extra things for us. They even sent round a joiner and decorator to repair the damage caused by us having to get the window taken out! Even now, they pop round if we need anything checked - others haven't been so lucky because they were super aggressive.
Confirm that the landscaping is finished before you start doing anything - we had no idea we were due to get a tree until we had planted a load of lavender exactly where the tree was supposed to go. The tree took 6 months to be planted.
Check silly things like whether the bath/sinks/showers have hot and cold running water. We didn't realise until week 3 that the bath didn't run hot.
Less positive - consider an alarm at build stage and be extra vigilant about locking your doors. There were several sneak in burglaries on our street within weeks of moving in and the police said that they were trying doors and windows in the hope that new homeowners weren't used to their properties yet.