TIP #1: If you buy building materials in small quantity you will pay full retail price. Instead figure out exactly what materials you will need. Include everything from screws to appliances. Make your material list look professional and take it to any large construction supplier like home depot or lowes. Do not talk to a clerk but go straight to the contractor desk or speak to a manager and tell them you are building your own home and would like the contractor discount for buying all the materials from them.
Most building supply stores will give you anywhere from 5% to 15% discount if you buy all material at one time. They may even throw in free delivery if you live within a certain mileage.
If you have to buy in small quantities go to the mom and pop building suppliers with your list and ask the manager for a discount if you buy all your materials from them over time. You will still usually get a discount and be supporting your local dealers.
TIP #2: If you are using solar (I hope) try to buy your panels in bulk for a big discount. Most panel suppliers will give 30% or more for bulk sales of ten panels or more and a smaller discount if you buy more than one. Talk to the owner if possible as salesman rarely have power to discount. Get your power controller and necessary wiring and even batteries from the dealer and get an even bigger discount!
TIP #3: Recycle whenever possible. Good used Doors and windows can be had for free or cheap from most window installers. Get double pane and insulated doors for exterior. They may need painting and might be different sizes but the savings is worth a little extra work.
Good used appliances can be had for free or cheap. Check out your local freecycle website, garage sale, city dump, or look for homes being remodled and make an offer. Sinks, toilets, cabinets, tubs, showers are always being thrown away so do some scrounging and don't waste money on new ones.
New propane appliances can be expensive but if you have or can buy an old rv cheap salvage all your propane appliances to outfit your home.
TIP #4: Design your home for efficiency. Consider how big of a home you really need. Smaller homes are cheaper to build, cheaper to heat and cool, easier to clean and lower in property taxes. Because people are looking for smaller efficient homes they also raise in property value faster than big inefficient homes.
TIP #5: Use the sun and passive energy. Situate you house to take advantage of the sun for winter heating and solar panels. Plant trees for natural summer cooling. Use overhangs to block summer sun and porches for cool resting spots. Passive air turbines instead of expensive air conditioning.
TIP #6: Go solar! There is a fed rebate of 30% for any size solar electric system installed by a professional installer. You can get this rebate even if you do the work yourself if you will contact an installer and ask them to design your system and oversee your work. get them to sign off on the work as being installed professionally and you can get the rebate. Many installers will do this and I do it all the time for clients. If you buy your equipment from them they can get you a bigger discount and they will give you valuable advice for designing the right size system for your needs. It may be worth a few hundred dollars to have their professional experience and you will save a lot in the rebate and having a correctly designed system.
TIP #7: Do the work yourself! Even if you have no building experience you can save a lot by having a knowledgeable builder use you for labor on your own home. Take a construction class or volunteer with a habitats for humanity project or your neighbors construction to learn the skill you need. Home construction is not difficult and most people that have basic construction knowledge can do it themselves or with a little guidance from a knowledgeable builder.