First of all the lot needs to be big enough to build your house. You will need to know what set backs, easements, and other constraints to your building exist on your property. Usually the city or county have this information readily available online.
Other concerns may include if the land is level and what type of ground you are dealing with. You may have plans for a basement and then find out that your property is full of rock and digging will be very difficult.
In our case the lot was the correct size and shape (1/2 acre) and our plans included a crawl space not a basement so rock was not an issue. Giving all the windows to Habitat for Humanity also saved us from having broken glass on the site after demolition.