Find the book you need. Once you are sure of the author, title, and ISBN number you are ready for the next step. This is important because most sellers will not give a refund for simply ordering the wrong book. For most books there are ISBN-10 and ISBN-13 numbers. I have always used and found success with the ISBN-10.
Compare prices. There will never be a website that always has the best price. Sometimes Amazon wins and other times half.com wins. I personally only use Amazon and half.com but many people have been happy with other reputable media companies such as overstock.com among others. Also, I typically use half.com. I do not think half.com is necessarily better; however; I want my eBay feedback score to get higher so I use half.com.
Look at the seller's feedback. I always suggest people should not buy from sellers unless they have a 97% positive feedback or higher. I know this score sounds high but the reasoning is simple. Why buy from someone with less than 95% positive approval when there are hundreds of other eBay users with 100% positive feedback. It is your money and you deserve the best. Also, look at the number next to the user's eBay name. This is their feedback score or the total amount of transactions the user has done with eBay. I would recommend not buying from sellers with a score less than 20.
Decide what condition you want the book to be in. Half.com has separated their book categories into brand new, like new, very good, good, and acceptable. Here is the link that describes exactly what all these conditions should mean according to the websites terms and conditions: http://pages.half.ebay.com/help/buyer/checkout.html. Amazon has the exact same condition standards and the link describing each one can be found at: http://www.amazon.com/gp/help/customer/display.html?nodeId=1161242. Amazon also offers a program called Amazon Prime. With Amazon Prime you pay $79 annually and receive: 1) Free Two-Day Shipping on more than one million in-stock items sold by Amazon.com. 2) Upgrades to One-Day (Overnight) Shipping for just $3.99 per item. 3) Two-Day and One-Day shipping usually apply across business days. Prime also offers special weekend and other shipping options for qualifying merchandise 4) Free Standard Shipping for eligible items shipped to P.O. boxes in the continental United States (excluding Alaska, Hawaii, and U.S. territories, possessions and protectorates) and APO/FPO addresses with U.S. zip codes. I have never used the program but it is probably ideal for the frequent user.
Decide how you want your order shipped. All users will offer media mail because it is typical and the cheapest and slowest way to ship. Media mail can literally take anywhere from only a couple days to as long as a couple weeks. Figure out when you really need your media. On half.com when looking at book listings, to the far right will say "Media Mail from WA" and will possibly have an icon that says "Get it faster" if the seller offers faster shipping.
Buy and wait. If the book takes longer than two weeks, first contact the seller and then contact the support group for the website. Amazon does have a refund and partial refund policy. You may return new, unopened items sold and fulfilled by Amazon.com within 30 days of delivery for a full refund. More information on amazon's refund policy can be found at: http://www.amazon.com/gp/help/customer/display.html/ref=hp_navbox_lnret_pol?nodeId=15015711. Here is the statement regarding half.com's refund policy. If you receive an item different than described, damaged, not of stated quality, or the package arrives empty, you can use Half.com's Email Forwarding System to contact the seller and resolve the issue. More information on half.com's refund policy can be found at: http://pages.half.ebay.com/help/buyer/buyerorderprob.html. Overall, Amazon's refund policy seems to give the buyer more insurance.