Learning About Fish Oils

about to start using fish oils. already i can see that “oils ain’t oils”, as there is a big difference in price at either end of the market, but they all list the same quantities of epa/dha. i know how good Flameout is but its very expensive here in Australia. also, all the articles ive read just talk about “fish oil”. can anyone point me in the right direction of some articles explaining what it is i should be looking out for when buying fish oil? i know i need to get this one right.