Just as you might walk through a real shop collecting an armful of tempting books, most online stores provide an electronic shopping basket. There's plenty of opportunity to take a title out again if you change your mind. When you're happy with the contents of your basket, the actual buying process may take several steps - at least the first time you buy from a particular site. If you are ordering by credit card, you'll usually have to create a password-protected account. Another complication is postage and packaging.
Most sites provide a choice of postage prices based on the delivery time.
If you want the books quickly, you may have to pay more. If you order several books at a time and not all are immediately available, you'll probably be asked whether you want the shipment to be held back until all books are available, or processed as each book arrives - obviously more expensive in terms of shipping costs. Before the final order price, including shipping costs, is calculated, some sites will ask whether any of the books are gifts to go to separate shipping addresses. Some even offer to wrap gifts for you, inviting you to click on the wrapping paper you want. Once you have the final price, most will give one last chance to confirm you really want to do it before the order is finalised.