Im flying a lott and this is what worked best for me.
Optifly.com for finding lowcost airlines that kayak won't find. Be flexible with time. Sometimes booking a flight within a few days that you want to go is a great option, sometimes booking far ahead is better. Checking multiple airports in your neighbourhood. Can save you a few 100$. Checking more airports at your destination. For example you wanna fly to Bangkok, also check Kuala lumpur, singapore and hanoi for example!
Goood Luck!!! And one more tip if you can have a direct flight or 1 stopover and your flight is direct 10 hours and with a cheapass flight with 2 stopovers 24 hours, consider this as a big pain in the ass....