The start of the home building process is meeting with the builder to get an outline of what is going to happen. You will have to sign a contract. Buried within this contract is usually a timeline for the project. There will also be information about what you can do if the project isn't complying with the term of the contract.
When everything is on schedule and going as it should, you might be able to sit back and relax. However, sometimes, things go awry in this process. A project that has been on time might be suddenly running behind. Other things might not be done like they should. When this happens, you might have to take legal action to invoke the remedies that are offered in the contract.
A builder who is bidding on a project should have the schedule padded to compensate for common delays like the weather or the time it will take to get specific materials. Therefore, barring an emergency, there isn't any reason why the home shouldn't be completed on time.
Some people think that everything is going great at the home site only to find out that it isn't when they visit it. This is one reason why it is a good idea to make weekly visits. You can see the progress yourself. You might also be able to find and point out potential problems early in the process.
If you find that the builder isn't willing to comply with the terms of the contract or that they aren't planning to correct defects, you might have to take legal action. While many cases won't require this, be prepared in case yours does.