The next house we have built -
we won't do any of the work ourselves - so many things still need to be finished still (painting mostly) and the time we spent doing it all, dh could have done extra work (at his 2nd job - realtor) and made the money to pay for it. But I

my tile!
We won't set a date for moving until we close on the new house. With unpreventable delays (concrete shortage - changing financing at the last minute) we had to move out of our old place, and lived here (thank goodness our builder is a good friend) for a week before we closed.
Have more electrical outlets put in outside - for lighting and my pond, etc.
Things I"m glad we did and would do again -
upgrade the AC, windows and doors - everything is double insulated, and the AC is more energy effecient.
Tile everywhere - love the easy cleanup compared to carpet!
upgraded the appliances to what I wanted and just paid the difference from what the builder supplied.
Don't be afraid to ask for any changes - if they are possible, a good builder will do them without a problem - or he'll explain why or help come up with an alternative.
DO research in your area about the builders!!!! Mercedes Homes in our area is one of the shoddiest builders - but they have gorgeous looking houses. But everyone I know has had a ton of problems with their houses!!! ANd they are terrible about service calls and getting things fixed. But they we in the top 100 of builders in FL (productivity) and rarely will you find anything in print about them being bad, but if you talk to people, you'll hear lots. Even the title company will have info from what they've heard about different builders! I'm soooo glad our friend is an excellant businessman, and everything I've heard from other people (his subcontractors, the title company, people in houses he built) have had nothing but good to say about him.