Only use Buy It Now ever.
Require Immediate Payment.
Not only are the fees lower for Buy It Now than for auctions, but there's no way for buyers to game you. The listing will sit until someone actually pays you.
As someone who uses eBay to buy specific out-of-print books, I vastly prefer the Buy It Now option, as long as the price is reasonable. I'm not really looking for incredible bargains, so auctions are just annoying.
With some items you might not know how much they're worth, but it's easy enough to determine the going price of a used iPhone.
Speaking of buy it now, I find it moronic that the buy it now button disappears when even one bid has been entered for the item.
This weekend I bid for an item, then 1 hour later decided that I wanted to pay the 10% extra for buy it now, discovered to my dismay that the buy it now option was gone, thought that the seller had manually removed it, got annoyed and retracted my bid, then saw the buy it now button come back (!) and then managed to buy it now.
I have no idea why they'd make the behavior like this...
If you know that Buy It Now disappears as soon as someone bids, then you're more likely to Buy It Now because if you don't Buy It Now, you can't buy it later; you can only bid on it later, and then you might not get it. So if you want it, eBay wants you to Buy It Now.
Only use Buy It Now ever. Require Immediate Payment.
Not only are the fees lower for Buy It Now than for auctions, but there's no way for buyers to game you. The listing will sit until someone actually pays you.