Perhaps the best way to lower your mortgage insurance bill is to increase your down payment to above 20%, which will exempt you from paying the sometimes outlandish PMI, an extra charge that banks place on low down payments as insurance against defaults.
If you have already bought your house, or you do not have a lump sum of cash set aside equal to 20% of the house price, you can sometimes negotiate mortgage insurance decreases by re financing to a higher monthly payment or a shorter payment period. Basically, if you can decrease the risk that the bank takes, you can usually negotiate.