When you are buying a new home, there are a lot of different things to consider. When you are building, you get to make decisions on absolutely everything, but even if it is in the stages of being built, you can still give your input and get some of the features you want. A lot of this will depend of course on what stage it is in though.
But if you are purchasing a home that is already built, but has not been lived in yet, you do have some leverage in your negotiations. This is especially true if the house has been on the market for a while and it is not moving, just like a home that has already been lived in before. But with a new build, you may be able to get them to change some of the features that you may not like such as the colour of the walls or the type of flooring in a room.
It is also still a good idea to get a house inspection even though the house is new. It will give you an idea of how good the construction is and if there are any issues that may have been overlooked during construction. All you need to do is watch home improvement shows to know that just because a home is new does not mean that there are not some problems with it. It is also a good idea to find out what type of warranties the home may have and what these will cover.