Lessons Learned - Building a House

We're about to start building a house but haven't signed our lives away just yet to the contract.
Has anyone recently built a house and if so, can you provide any advice based on the lessons you learned?
It has certainly been challenging so far - getting the builder to do things in a timely manner like plans, engineering, soil tests, estimations etc.
My biggest lesson thus far is that whatever the house costs, add 40-50% again for all the rest of the stuff they don't count in their "display" prices. This has been a complete JOKE!
I've also quickly learned that they add their own margin on to every sub-contractors price.
I want to get a completion date in the contract (eg 26weeks) with a penalty clause if they run over time on that. I'm not holding great hopes here but any tips or tricks would be greatly appreciated!
Has anyone recently built a house and if so, can you provide any advice based on the lessons you learned?
It has certainly been challenging so far - getting the builder to do things in a timely manner like plans, engineering, soil tests, estimations etc.
My biggest lesson thus far is that whatever the house costs, add 40-50% again for all the rest of the stuff they don't count in their "display" prices. This has been a complete JOKE!
I've also quickly learned that they add their own margin on to every sub-contractors price.
I want to get a completion date in the contract (eg 26weeks) with a penalty clause if they run over time on that. I'm not holding great hopes here but any tips or tricks would be greatly appreciated!