1. Small is subjective. Build what makes sense.
2. Be frugal. Being frugal means being modest not a cheapskate. Stay away from subpar materials. Be willing to pay for quality and save money by limiting your demands.
3. Reuse the right stuff. Salvaged materials can be great or utter garbage. Reuse materials that will enjoy and deserve a useful, long life. Don't use materials just because they're repurposed or inexpensive. Example: You're not doing anyone a favor by installing old, leaky windows and doors.
4. The construction industry has an embarrassing history of approving and subsequently banning products eventually shown to be toxic or grossly subpar. Most prefabricated goods are loaded with glues and other chemicals and in general won't last as long as the traditional materials they're intended to replace. They also often require intensive energy to manufacture and ship. Not all prefabricated products are equal. Some are worthy, most are not. Investigate your materials and know what you're putting into your house - and ultimately your body.
5. When possible use local materials if they're of good quality.
6. When needed hire local contractors if they do good work.
7. Create beauty! Design is one of the most important factors when it comes to sustainability. People are more likely to care for and preserve a house built with care and attention to detail.
8. Build efficiently and build to perform efficiently. If possible, have your work tested to be sure you're achieving your goals. Verification, which tests actual performance, beats any certified checklist. Keep in mind that many certification programs, including the much touted LEED, don't even test performance! Invest potential certification money directly into your project and do good work.
9. Use the least (and as few) toxic materials as possible.
10. Reject much of what passes for quality construction and design.
Shawn A. Dehner - THE small HOUSE CATALOG