My policy just re-upped in June, and I spent a large swath of April/May calling around, trying to find a better rate, so I've just been through this, and here's what I learned.
If you're employed, look to see if your workplace offers discounts with certain providers, and check them out first. Insurance companies really like payroll deduction. If you have auto insurance, check to see if you can get a discount through bundling with the same insurance company. Otherwise, gather a list a companies and grab your phone.
When you call the company, the insurance agent will ask you a long list of questions -- everything from the square footage to what the walls and floors are made out of. This is to determine the "dwelling/replacement cost" of your home, which is how much they'll pay out to rebuild your house if it were to get destroyed. If that number is too low, your premium will be lower but you will be under-insured -- as well as vice versa -- so you want it to be as accurate/realistic as possible. It sounds like you're building your own, so you should know exactly what this figure should be.
The discretionary parts of your policy have to do with deductibles. Most policies have a $1k deductible, but you can bump that higher (ours is $5k). There are also medical payments and liability, which you can bump lower if you wish. I think we got the lowest medical payment offered (it's not much anyway so we're fine with assuming the risk ourselves), but kept the higher liability because we actually have enough assets to sue over if an accident happens on our property. If you live in a hurricane-prone area, there's also an option for a lower or higher hurricane deductible which is a percent of your dwelling cost. There might be other disaster-related stuff depending on where you live.
The most important part, though, is to call multiple companies and compare their quotes. I actually spent weeks on this, haggling back and forth. A lot of places will "magically" find a new discount for you if it looks like you might not go with them, so don't be shy. Insurance agents earn a commission by signing clients, so they really want you.
Lastly, do NOT let your policy go on autopilot for years at a time. The insurance company will automatically raise the dwelling cost each year, along with your premium, so ask them exactly what the calculation is so you know what to expect, and renegotiate if the cost rises above what's reasonable or competitive. (This is where I erred -- I let my premium balloon way out of control before I wrenched it back down, and April/May will forever be "review insurance month" for me going forward. :P)
