Be straight-forward on your ad. Let people know what you do or what you are selling don't just put a picture of something amusing and hope people will click it.
Don't promote any false advertising such as "Get Rich Overnight" or anything that leads to false promises. Too many ad campaigns are based on that and therefore get rejected by Facebook and other advertising platforms.
You want to make sure you have the right targeted audience and also the right keywords for your ad.
No sexual or pornographic images for your campaign. Facebook will turn them down but also that will give them the idea that you're not serious about marketing on their site.
To get better conversions on Facebook add some incentives like something you will offer in return for the user buying your product. Maybe a free e-book or guide or something clever.
Try and make your ads social. Meaning don't make them look like boring ads but something like an interactive ad, like comment ads. They make the ads look like a conversation and ask you for your opinion on their product or service.
