Successful book sellers - what are your best tips?

I just sell the occasional book of mine after reading it so not on a major scale but some advice I have...

I've been using NZ post. I mostly sell novels and was using the previous prepay S ticket. Its dimensions allowed for up to two average size novels. I'd state in my postage that I could send up to two books for that postage which often led to customers buying multiples, since it was easy to see they could combine. Its harder to figure out the dimensions now the labels are volumetric but I think if you use the rate finder and pay online the dimensions still favour multiple books. Otherwise Pass the Parcel's pricing is quite good. I always use them when people buy four or five books and they can travel in their larger bags. Their box rates are good and their maximum weight allows for a lot of books compared to NZ post.

Ways to minimize listing costs - save up your most likely to sell things and list them all in the same week. If you have anything you don't mind clearancing for $1 reserve list it then too. You'll get five free listings for every sale over 10 for the next six weeks so if you can get a good number of sales in a single week every six weeks it reduces listing costs. 

Definitely use My Products. 

Include a description of the books subject - plot if its a novel. Basically what's on the back. People can google it but don't like to. 

If selling novels people like to know the size of the book - standard paperback, trade paperback or mass market. Photos from multiple angles are good. Always include the spine.