It took me 2 weeks to make a sale. You just have to keep modifying your listings and prices until you figure it out.
It is also helpful to do an eBay search for the items that you are selling, as if you were a buyer. Look at what your competition is offering, and see how you compare.
It is also helpful to do an eBay search for completed listings on the items you are selling - maybe there just isn't a market for them right now.
It's a lot of trial and error - at least for me.