First, I'm new to the forum and wanted to thank all the expert contributors, contractors, installers, and homeowners. I have learned so much from everyone and hope to contribute once I gain some experience and real-world metrics from my own construction project.

Second, I thought it would be helpful to start a thread with a "sticky" best practices or FAQ for those doing new construction. This would be similar to the "what to ask contractors" for geothermal heat pumps that I also found very helpful, but geared towards new construction where you arguably have some more flexibility. Let's assume someone has already decided to use a ground source heat pump for new construction, for cost, efficiency, "green", or whatever purposes. What should he or she do to get the best possible result?

Finally, here is some of my background: new construction second home in upstate New York (so typically higher electric and fuel costs; mixed use but generally heating is a bigger deal), no natural gas availability, ~2,000 sqft structure with basement, lets assume no constraints on property space for loops. What are obvious "best practices" for a situation like this?

Here are some of my general thoughts, culled from a variety of sources. Please feel free to add/update/change/correct. Thanks!

1. First thing is to economize your power usage. Saving power, being green, is a lot harder if you're being wasteful with energy in the first place.
2. Another first is to construct an efficient home! Nothing beats good insulation, very efficient windows, smart placement and orientation of your home, and so forth. These also cost very little if done properly, with big impact. What are other "no brainer" considerations on this front, besides insulation, windows, etc.?
3. Proper system sizing given your home, location, usage is critical. (Ton of posts and information on this, esp. for specific situations). Don't oversize!
4. Make sure duct-work design and sizing (if using forced air) is optimal and integrates into the overall system... it's more than just picking out a heat pump unit.
5. Consider desuperheater to recycle waste heat to supplement domestic hot water.
6. Make sure the system is properly spec-ed out to qualify for federal and potential state tax refunds.
7. Consider 2-stage unit not just for more economic, lower stage operation but to maintain consistent, whole house air conditioning, hot water assist, etc.
8. The installer (installation quality, service guarantees, support and follow-up, etc.) is far more important than the specific brand or particular marketing element, i.e. all top manufacturers make pretty good heat pumps now.
9. Simple horizontal loop is probably most cost-effective when you don't have space constraints. Don't forget to consider future in-ground swimming pools.

What did you end up putting in your home?

I haven't yet! Just closing on the land right now, talking to vendors with my builder (who has traditionally not used geothermal in his builds), and trying to get a feel for costs.

Actually, that's a good topic... how do you even go about getting cost estimates, or comparing prices, for new construction when there might only be floor plans? How do you determine sizing, and/or whether or not a proposed price is reasonable?

Determining if proposed prices are reasonable is done through multiple estimates.
One can perform a manual J heat loss calc from blue prints.
As a matter of fact it is a good process to educate yourself on as you can compare the value added of added insulation et al by pct of the heating load reduction (which equates into heating bill pct reduction).
More insulation = less heat plant and less duct or radiation system as well as lower heat bills.

1) after a first months bill, shop for other suppliers rates on utility.

2) a quick idea, really quick in N Ohio cold spot that hit -22 in 1994 and usually -12 is typical day or 2
and
balance point for electric strip is ~ 7-deg but customers want to 5 below frequently
and
never over-sizing with multistage units, 'cause lower stage can be for cooling...
~ 1/4basement @ 250, and half the 2000 2 1000 ~ 1250 cfm/ 400 a loose house on 3 real compressor tons in cabinet.
2stage
or the smallest H-T (below) Dual Compressor ~ 40k for some rated's "SIZE 4 'tons' " but put on a 4-ton loop and a 4.1/2-5-ton loop if you can excavate or horizontal drill inexpensively...
(Engineering spec'd 6" insulation just 30-years ago)
BUT :
Is Hot Water an issue with spa and pool and 6 people?
On Demand Priority HW is with GT a 100% heat-reclaimer and loop pump shuts off.
Hydro-Temp.com
or
TETCO phase4 Enertech (GeoComfort/Hydron)

up to 4zone board wireless Palm(tm)-Programmable is in the H-T

all on a one-pump circulation (even if 5-pipes in the ECL Earth-Coupled Loop.