Do not book with Webjet. They are a fraudulent operation. I canncelled my wifes ticket 3 weeks prior to the flight and requested the taxes portion of the ticket. Webjet refused. Airlines will refund the tax portion if a flight is not taken as the tax is not paid to goverments until the flight is taken. As a result of Webjet refusing to refund the taxes they can pocket the money as additional profit.
Look for promotions: Most airlines have special offers almost all the time. These offers are usually valid only for specific destinations and for specific dates (or days of week). If you are flexible on dates, check "what is on sale now", to get the best price! If there is no discount on your desired route and if your dates are flexible, you can wait for 2 to 4 weeks for a promotion on that particular route.