That's really good advice from Richelle!
Before you start looking at traffic generating avenues such as social networking and so on, start at the very start, and that's your listing. I would also suggest, in association with what Richelle has, checking the sale through rate of the product.
You need to know the sale through rate of a product to know if your sales are in fact up or down, as that is a strong trend line to follow. High sell through rate, then you should be getting better sales. Very low sell through rate, your sales may well be as good as anyone's, it's the product it'self that is the issue.
Well, product or something closely related to the product. So now you look at other factors, such as how competitive you are on price and service with other sellers and so on.
It's about making your listing as sharp as possible, cover all the angles so that nothing is left to chance. When you have that down, then is the time to start looking at ways to generate more traffic, so your effort in doing that isn't a complete waste.