There are a number of ways to try and figure out if a hub article has revenue potential.
Firstly, write about something you have a hope in hell of being ranked for in Google. You want traffic and pages views. One of the best ways to do that is by being ranked on the first page of Google for your targetted keywords.
There are more people using Google everyday than there are on Hubpages. Also Google traffic is more likely to be targetted traffic and actually interested in what you've written. They can also click your ads, whereas Hubbers are told NOT to click your ads.
I tend to try and target things that are very popular, but with less competition on the search engines since it's relatively new. This way I have a chance of ranking for a keyword that gets decent levels of traffic as there aren't millions of competing pages. However, most of these hubs tend to be a fad or are trending in nature, so the traffic will and does drop off. For example - new video games, movies, books, toys, gadgets etc.
Sidenote: The CPM tends to be lower, but you are hoping to compensate for this with the higher levels of traffic.
If you want to go for evergreen content, that will earn money for years to come, this tends to be more competitive. To combat this, you should target longer tailed keywords or keyword phrases in order to get some Google love. For example, you are unlikely to rank for "weight loss" as it is too general. However, you could rank for a specific type of weight loss more easily by targetting a sub-niche such as "10 tips to lose man boobs forever" or "the secret to never having bingo wings" etc.
Unless you are lucky, or find a great niche, you'll probably get less traffic per article. However, traffic should hopefully be consistent or continue for years to come.
Sidenote: The CPM is likely to be higher, since these are more competitive terms, but you are likely to have less traffic.
Best of Luck and I hope this helped.