I sell books mainly on Fishpond I have found I get a higher price and I find the whole process easier. They charge the customer $4.99 postage on your behalf. They take care of the payment and you receive it plus the postage money within 14 days of receiving a sold email. One disadvantage of this system is they take 10% of the total price, including the postage, so you only really get $4.50 postage.
Here are my tips and what I do when looking for books to sell and when listing.
1.) Sell slim books. Ones that fit in A5 or A4 envelopes are best as they are the cheapest to post. If they do not fit in an envelope, try to get books that weigh less than 500g so they can fit in a prepaid satchel. Much more than this and it will cost you a lot to post, and often works out to not really be worth selling the book.
2.) Stick to certain genre’s. I have found bestsellers don’t really work because so many people are trying to off load them. Books on finance, self help and relationships I have found sell the best.
3.) Check op shops and garage sales for cheap books to relist. You can often get them for 50c - $1 and resell them for $15 or more.
4.) Keep the books you are selling separate from your own books. This way you wont accidently lend one you have listed and risk not getting it back.
5.) Have a separate account for book payments to go into to make it easier to track.
6.) Keep proper records. A spreadsheet listing the book, sale price, fees, postage and profit helps you know whether it is worth it for you or not.
There are a few disadvantages to selling with Fishpond. The long time it takes for them to pay you and they are rather hard to contact. I seem to do OK with selling through them so I will continue for now.