Facebook advertising performs significantly better than many other forms of user experience that I've tried. For email marketing I've found anywhere around 1-2% is pretty average and that's very similar for Google AdWords.
For Facebook advertising I've found 2% to actually be a low performance number and have seen highs above even 10%. That's pretty incredible to have 1 out of every 10 viewers click on your ad!
What makes one ad more effective than another? I wish I knew for certain but marketing is more of an art and has lots of uncertainties with changing variables. More important than that you want the ad to be relevant to where it leads or else you're only paying for clicks.
If your ad is running at a lower percentage of clicks that you're used to seeing here's a helpful flowchart from Facebook that can aid in figuring out why your ad might be underperforming.
If you feel you're doing all the bidding right and your audience size is good then you're likely needing a design or content change. Choose a good color that sits well on a white background such as orange or green. Though as mentioned before make sure the color choices are still relevant to your own branding so that the viewer understands they're arriving at the correct location after they click.
If your ad is a photo make sure the quality is good. Facebook recommends a size of 1200px by 628px and even though most ads appear much smaller than this a larger size will still help them appear better on certain screens.
Consider re-wording the text that appears above and below the ad. Often "less is more" with ads so don't feel you need to fill the entire 90 character limit in the text above… same goes with the text below.
Test your ad too. Facebook is being accessed by a lot of different devices with a lot of different screen sizes. Probably the most significantly different one from a desktop are smartphones. Test how your ad looks on an iPhone or Android and look to see how eye-catching it is. Have a friend or colleague view your ad as well and see if they have any valuable input.