Get a realistic financial picture of the whole project: the land, permits, roads, septic systems, etc. The biggest mistakes people make seldom involve their own workmanship. Know all the facts, all the costs before you draw up plans.
Construction loans are difficult for new builders without track records. Walk into a lending institution with plans, materials lists, price, subcontractors estimates, and schedules in hand, and be prepared to prove your overall financial stability.
Have a construction guru available. Get to know the building inspector for your area. You don't have to wait until the house is finished. Make him a part of your project from the beginning.
Don't buy retail. Remember, you are acting as your own construction contractor. Buy all your tools, materials, lumber, etc., at contractors' or volume discount prices. Keep shopping where the pros shop, until you get a good price.
If you're remodeling, make it compatiable with your existing structure. And study your own lifestyle before designing anything. Where do you want a door, a window, a light switch? How many closets? An oversized bathtub? Know ahead and you can have the refinements that suit your family, or your individual needs.
A word to couples. Be sure your relationship is stable before launching such an intensive project. The strain of building can test a shaky marriage by exaggerating its faults. A good marriage gets better, mutual admiration abounds.