One way to find ads that are likely to be doing well, is by finding the top affiliates, and on each one of the top ones, click on “Ads” to see the ads they are running. Since these people have run thousands of ads, it’s likely they know what they are doing, and their ads will be (for the most part, other than brand new tests) profitable.
Another way to find top converting copy is to go to the Popular Copy report, narrow down by your niche (and optionally by timeframe, if you want to know what is working right now), and for the top copy, click on both “View Ads” and “Copy Info” to get more info about that particular copy. Something used on multiple fan pages is guaranteed to be getting good results.
Finally, you can just go to the “Search Ads” section, and search for ads matching your criteria. For example, if your niche is Weight Loss, you could select “Niche = Weight Loss”, “Min days running = 5”, and most (if not all) of those ads will be profitable, as they have been running for over 5 days. If you click on one particular ad, you can find more info about the creative, copy, landing page, affiliate id, offer, etc. and identify other related profitable ads (from the same fan page, same affiliate, same copy, etc).