Couple of thing's I've discovered.
Buy it Now with no additional quantity entices buying, especially from items typically purchased by female consumers. I sell high priced items this way. I feel that I can create increased value by selling only one at a time. With many listed, the value of the item actually decreases. I find this common in things such as Purses and Shoes. Multiple quantity, such as "12 Sold" on listing increase business to consumer confidence. It shows a consumer that "People want this, and I should want this too." I find this common with Pants, Dresses, Shirts, Electronics, Sex Toys, etc. A blackhat method that would increase sales this way would be to buy your own items from different accounts. "1 Sold" can become "132 Sold" and although I can not confirm this, but I feel that this increases your items ranking in eBay's "Best Match" algorithm.
When you sell plain ol' items you pick up at a yard sale or something, I have had better conversions from items that didn't have elaborate item descriptions and templates and stuff. A couple good pictures is all you need, not an overly drawn out description of the item. People hate reading, and cutesy colors, pictures, and logos distract from possible sales.
Make as FEW links as possible. Buyers now a days have an ADHD mindset, and click around. After several clicks, they will move on to something else. Either completely different items, or off eBay totally to check their e-mail or something. Gallery image scroll bars commonly seen by Auctiva are the worst.
Be either the cheapest or the most expensive. You either want to be a Walmart brand, or a high end Name Brand. eBay makes it WAY too easy for people to compare prices side by side. Being cheap (and sometimes undercutting) increases your number of sales, but usually does not increase your profit. Being the most expensive can sometimes increase value. You make one sale, but it would probably be very profitable.
Don't think small all the damn time. Don't let a shitty buyer leave you negative feedback. Either cough up the money and bribe them, or try to legally scare them.