For three years our business had no income, just expenses, and we got GST refunds every two months. They will question big refunds, like when we claimed for the GST on the land we run the business from, but if it is just a couple of hundred dollars here and there they know you will make it up eventually. We eventually elected to have our GST done by our accountant, hopefully that will make the IRD less inclined to question it.
As Moorf said, claim for household expenses too. We claim 25% of our phone, and power bills.