Always get more than one bid and check your potential contractors' references. Compare the fine print of the quotes and ensure their past clients were satisfied with their work. If they don't provide references right away, ask for them! A confident, reputable contractor will be willing to provide references.
Building a slightly smaller home can save a lot of money. If, for example, the cost per square foot for your home build is $120 and your plan is for a 2000 square foot home, that will cost you $240,000. Subtract just 300 square feet and make a 1700 square foot home instead and you'll save $36,000.
Help with the work. Being willing to take on certain tasks yourself will save your contractor time, which will save you money on labor. Even if you aren't the handiest person, there will always be a number of simple but time-intensive tasks that you can do. Work out an agreement with your contractor to take care of those tasks.
Source your own materials. In many cases contractors are able to get better prices due to their agreements with manufacturers or by buying in bulk, but in some cases you can save money by finding deals on appliances and other necessities at local home improvement stores. Ask your contractor the prices of the appliances or other components and check around for better prices!
Salvage or repurpose materials. Have lumber sitting around from a barn teardown or other project? Use it! Barn wood is highly coveted these days for its durability and rustic characteristics. Anything you have that isn't being used can be repurposed to prevent having to buy it again!