Business offline and online is part art, using your imagination in response to customer needs, but also part science. The science part comes from running marketing tests and tracking the results. By running multiple tests, you learn better what works and what does not work. This is important because what works for your unique product, with your unique target audience, with your unique selling proposition will not be the same that works for someone else. Learning from others will help you learn how to make smart tests, but the tests in the markets are the only way to know if a tactic will work for you.
Most good ones do.
Another simple solution would be to set up the customer on an autoresponder that sends out multiple messages at predetermined times, so that you lessen the manual work, and avoid forgetting to send the messages. Beware that the customer may perceive these follow-up messages as SPAM if they have not explicitly requested to receive these messages. The concepts of aisle displays and the strategic placement of impulse items can be applied to online stores to dramatically increase sales. The response of your customer, e-mail marketing message receiver or web site visitor will be greatly enhanced if the message is something the viewer is interested in. The web marketer has the ability to learn what the visitor is interested in by following the items clicked upon during the visit.