re: Things to ask home builder before signing a contract?

A lot of what you do will be allowances. It will be incumbent on you to do your research beforehand.

Extras to add IMO. (I designed my house btw).

Truss design over the garage to be open so you can use it for storage and easily walk around.

Attic lift. The utility of this cannot be overstated.

Privacy fence if you want one. A lot of builders don't do them. Personally I bought the materials myself, a lot of treated is garbage and you cull a good bit.

Outside plugs and faucets. Look at your plans and think about how you'll move hoses or cords around. Make sure you have enough of them and have that noted.

References, particularly anything they currently have under construction you want to see it. If they won't show you pass and find someone else.

How do they do their headers. I've always looked at that as a key to how good the framers are.

HWH size and/or type.

Include hard wire internet/cable everywhere.

Who does their cabinets. This will make or break your house. Research them thoroughly.

Hope that helps