First of all look for all the books around your home that you no longer want. Once you have your books at the ready then register on the Amazon site which will literally take ten minutes or so.
Listing the books on the site is extremely easy as you enter the international book standard number and it will automatically bring up your book. You then can see the market price for your used book.
I would recommend entering your book price at one penny less than the nearest person which ensures you get a low price tag next to your book. You then just click and complete your listing. Amazon will then send you a sold dispatch now email when the book is sold and you mail the book to your customer.
Once you need more stock I recommend looking at the local charity shops and libraries. Also car boot sales and fairs are very good too. I have bought books for 25p and sold them for 20 pound and this happens weekly.
Not every category of book will sell extremely well so it is very important to avoid modern fiction titles. There are literally thousands of used books in this category on amazon and you will not be able to generate income with these types of books.
You should really be looking for older books with a hobby connotation. Good examples of these could be music, religion, self help, military, arts and crafts, sports and poetry to name but a few.
It is very easy to get the hang of and in time you will easily be able to identify what sells and what does not sell. I also personally sell dvd's online too but you must make sure that your dvd works before sending out to a customer because good customer feedback is very important in this business. Having said that dvd's are fast moving items and can easily make you a lot of money.
If you have an amazon library online of about one hundred books or so then you can be expecting to sell about 30 books or so a month. When you reach this level of sales then it makes it worthwhile to become an amazon book seller. This costs 25 pound a month but also cuts the 85p charge that amazon puts on your account every time a book sells. Of course Amazon needs to make some income from the arrangement with yourself but as you can see the 30 book per month and over limit makes it a viable business decision.
Another top tip is to try and keep your books small to medium in size to save on the postage costs. Amazon are quite generous and will give you a good postage allowance when selling your books but on very large books you will actually lose out.
Having said that school textbooks and educational books are very good sellers and can attract prices over 20 pounds or so therefore I would make an exception for those type of books.