It works because the banks generally work out fortnightly payments to be half of the monthly repayment. If you divide the months in a year by fortnights, you will end up with two fortnights left over, which effectively means you will pay 13 months worth of repayments, rather than the 12 you would have if paying monthly. You hardly miss the few extra dollars it costs you overall each month, but you will notice the savings.
Another popular strategy is to sink any pay rise, bonus, or tax return you receive straight into the bank. You are managing to live on your current salary at the moment, therefore any extras are better spent accumulating interest in your savings account, or reducing interest on your home loan, rather than on forgettable expenditure if the extra went into your pocket.