Mistake #1 - Promoting the wrong offers
There are many things you can run on PoF, but if you are getting started you should go with the easiest campaigns possible and avoid the more complex ones.
That said, you should promote niche dating sites such as Christian dating, Jewish dating, gay dating, black dating, asian dating, senior dating, etc... Avoid general dating sites, because people on PoF already have a great general dating site that's completely free: PoF! Why would they sign up for another general dating site that has less members and isn't free?
On the other hand, a niche dating site can be more specific for your audience and offer them something more interesting than the service they are already using.
Regarding other niches, it's possible, but, again, you should keep it simple and go with easy campaigns. PoF is a dating site, everybody there is interested in dating, so why not to start with dating?
Mistake #2 - Using only small ads
I've noticed that most beginners are afriad of using the small banners (310x110) or even the IABs (when they are unlocked), so they start testing only with the small ads.
That's a mistake. The small banners often times have a better performance than the regular ads, and the same applies for the IABs. So, give them a shot, don't be afraid to test the other ad formats with your campaigns.
Mistake #3 - Wrong targeting
PoF has a bunch of targeting options. Use them.
Make your campaigns specific, use angles. Target short men when promoting an asian dating offer and tell them that asian girls prefer short guys, target women with a low income and say that you have a site full of rich guys who are feeling lonely, target people with an athletic body and tell them that only people who are in shape are allowed in your site... there are endless possibilities, so be creative and come up with effective angles.
Mistake #4 - Making unrealistic claims
People are getting smart. They are already used (tired) to the exaggerated ads promising impossible things. Don't underestimate the intelligence of your audience.
Don't tell someone that they will meet 1,000 girls in your site who will be killing each other to go out on a date with them tonight. Everybody knows that, unless you're Dwayne Johnson, it's not going to happen.
Make realistic claims, focus on real benefits. That will make the ads and offer look less suspicious and people will be more likely to sign up.
Mistake #5 - Wrong testing
Testing a campaign isn't just to keep the campaign running until you run out of money.
Testing a campaign is making changes and comparing numbers.
I see many people trying the same type of landers, ads, etc over and over again and then complaining about the bad results.
When something doesn't work, change it. Testing another landing page isn't just changing the color of the background, it can be also changing the approach, the type of image, the organization of the elements, etc... Makre real changes instead of just insisting on what's not converting.