Pay special attention to your customer service during the holidays. Often the influx of orders can run you off your feet and it's easy to ignore the most important part of selling online, service.
Providing your customers with service excellence will not only nicely finish off their first transaction, but entice them to become a loyal customer and purchase from you all year round.
Pass on your standards to all staff involved in your business. Make an effort with every part of the order process, e.g. gift wrapping should be neat with good quality paper, make sure all products are in the box and don't forget your business card and a coupon for their next purchase.
Even a personalised "thank you" goes a ong way. A happy customer is a returning customer.