Watch them. How are other content creators in your niche utilizing advertising? What types of ads do they use? What are they promoting? What do they talk about repeatedly (if you keep seeing the same affiliate product show up again and again, there’s a good chance they’re making good money from it)? If you see a product or service they talk about that jogs your memory and you can ethically promote it too, find affiliate information by the methods described above.
High ranking metrics will result in getting your site on the top position of several charts such as Top Alexa sites, Top WOT sites and so more. People usually go through these lists to discover new sites and hence you will be getting referral traffic as well. Who knows? Some of those traffic may be your next big client or loyal reader of your blog.