Direct marketing stresses direct communication, measurable factors and testing, and a call to action. It is the focus on testing and evidence based decision making and effectiveness which differentiates direct marketing from institutional, mass advertising or image advertising.
It's really a different kind of mindset from typical marketing, but one very well suited to interaction design grounded in user testing.
First off, "know your customer" is not the trite, nice sounding blather it is elsewhere. Because you are not trying to entertain, brand or do anything else but generate a response. And that won't happen with any kind of effectiveness unless you target and profile a potential customer.
Contrary to popular opinion, rabidly spamming random people with zero interest in the offer is not direct marketing. The goal is a response you intended to get -- not death threats.
Next, develop a unique selling proposition (USP). A USP differentiates you from the competition and gives a reason prospects should buy from you, not a competitor. The better USPs also fit in a reason to buy now.
"Fresh pizza delivered to your door within 30 minutes or it's free" would be a USP.
"We offer web hosting to everyone ...for any reason" is not a USP.
Benefits, not features, rule. So announcing your feature list, the very same features 90% of competitors offer is quite wide spread, but not direct marketing. A useful rule of thumb for knowing the difference between a feature and a benefit: Features would exist without a single customer. Benefits only happen with
use, and achieve a specific goal for a target user.
Making benefit rich copy as rare as hen's teeth because so few want to admit they can't have 100% market share by being everything to anybody. The trouble is people don't feel you are offering something to
them, so such offers turn out meaning nothing to anyone.
Finally, you have to call for the reader to
act. In copy, there is a formula: Attention, Interest, Desire, Action. Design can assist your call to action with buttons, form design, and other persuasive design techniques (yes, there is a field called captology or persuasive design).
Direct marketing for response is much more than an e-cart install, an emailer, or an automated script; it's more a state of mind. One which a lot of developers will find customers -- results driven customers -- respond well to.
Related:
Never Get Involved in a Land War in Asia (or Build a Website for No Reason) is a good starting point for developing a direct marketing mindset. Most sites use excuses, not reasons requiring a specific objective.
Five More Principles of Effective Web Design applies the AIDA acronym to web design. The vast majority of designers know how to grab attention ...just not what to do with it once they have the site visitor's attention. Most attention grabbing gimmicks have nothing whatsoever to do with the client or the reason the visitor is on the site. This makes it unlikely such stolen attention will translate into interest, desire or action.