Get very high quality fish oil and take 1 or more capsules a day. The low quality crap has kelp and other impurities that make the same types of fatty acids found in fish oil, however kelp collects other impurities so the cheap fish oil capsules contain a higher percentage of impurities and non-fish oils, and that's just not good for you.
The way to tell the difference is if you take 3-4 of the good capsules, the worst you'll get is maybe a burp or two half an hour later. If you take 4 of the cheap ones, you'll be burping fish for hours and have other intestinal "issues" as well.
Even one a day ought to help the cholesterol though, just get the good stuff. One way to tell if it's high quality is to see if they track the bottles by production lot. If they don't, then their quality control isn't up to pharmecutical standards. If they do, including lot number and manufacturing facility right on the packaging, then there's a good chance they pay attention to the quality and aren't adding fatty acids from kelp in along with the fish oil.