The worst that can happen to you is to lose your customer during the check-out process.
How to avoid the most serious obstacles:

1. Availability
   Inform the client before the check out process that an item is currently not available. There is nothing worse than filling in several forms and being informed in the last minute, that you currently can not purchase the product. Show the availability status on every product page.
2. Payment methods
   Offer several payment methods such as PayPal, Visa and MasterCard. This increases your chance that the client will continue the check out process. Inform him that the data is transmitted secured. In case you have received a “Trusted Shop” certificate, display it prominently. It increases trust.
3. Back Button
   You just quickly wanted to go back one step to check one entry field and then all your previously entered data was gone. Make sure that the customer always can go back and forth without loosing any entered data. It is tedious enough to type in your card number once.
4. Credit Card rejection
   Imagine your credit card is rejected. That is always a very unpleasant moment. Tell the client with a friendly easy to understand error. Inform him of what might have gone wrong:
   - The address needs to be the same as on the credit card.
   - The name needs to be the same as on the credit card.
   - What is the CVC Code and where can he find it.
   - Could it be that there is a daily limit on the card? (in case you are selling expensive items)
   - How can he reach the hotline in case it still does not work.
5. Forced registration
   Don`t force your customer to register in order to simply buy something. To remember his contact and financial data is an extra service you can offer and the return client can benefit from. However, many customers might not be return customers and some simply hate to have to recall login data or to have their data saved and accessible online.
6. Cross selling
   Cross selling is great, we all agree. However, don’t be too pushy during the check out process. Customers might either get confused or really turned off. Do your cross selling when show casing your other products or after the check out.
7. Hidden costs
   Honesty always pays off. Show your customer as early as possible fees for shipping, taxes, handling fees and so on. Nobody likes unpleasant surprises at the very last minute.

Check out the entire series:
Part 1) Navigation and homepage
Part 2) Product overview
Part 3) Product detail page
Part 4) Search
Part 5) Check out process

To come:
Part 6) The shopping basket

Having a powerful search engine within your site might be the best investment of your money.

The most difficult task is to define the technical requirements your search engine needs to fulfil. Once you have decided on those, 3 major points for the design of your search interface are:

1. Place the search clearly visible and offer the search entry field on every page.
2. Make the general search interface as simple as possible. You might want to add an additional filter option such as availability, gender or product category.
3. Don’t go overboard with defining the detailed search. Studies show, that not too many people ever use it.

And what are people looking for in the result page. 5 points

1) Inform the users of what they typed into the search field.
2) How many results were produced
3) The results should have a clear title and a short summary
4) Show where the result is placed within the site (URL)
5) Let the customer filter the results (i.e. from cheapest to most expensive)

e-bay for example lets you filter the search results, shows an image and a title and in addtion even offers the option to save the search criteria.

Check out the entire series:
Part 1) Navigation and homepage
Part 2) Product overview
Part 3) Product detail page
Part 4) Search

To come:
Part 5) Check out process
Part 6) The shopping basket

Once your customer is on a product detail page he made it half way. Now it is important that the customer can get an understanding and feeling for the product, try to make it tangible. 5 points which are important for product detail pages:

1. Good product visualisation is crucial. Show the products from different angles, the front and the back and allow the user to zoom in. Show different colour versions. Close ups are especially important where the texture or surface of the product is important such as clothing or jewellery – make the product as tangible as possible. Let the user “touch” it.
2. The presentation on all the product detail pages should follow the same pattern throughout the site so that the user can learn your site and get accustomed to it.
3. The most important product details need to be in the visible area without having the user to scroll down.
4. This is also a great time for cross-selling: Show the customer what other users bought and make pro-active recommendations. It is better to make recommendations on behalf of the behaviour of other users than by yourself. Say: Customers who bought A also bought B instead of We recommend B for people who are interested in A.
5. The user needs to be informed about the availability of the product. (in case this has not happened on the overview page yet).
6. If your delivery times are much faster than business standards or much longer mention it.

One really good example is again Esprit.

Sizes, colours, product illustration including zoom and front and back images, addtional product information, availabilit, cross-seeling all is in place

Check out the entire series:
Part 1) Navigation and homepage
Part 2) Product overview
Part 3) Product detail page

To come:
Part 4) Search
Part 5) Check out process
Part 6) The shopping basket