Talking with many marketing experts, you'll hear you must reach prospects between three and thirty times. With internet marketing, you don't know who you're reaching consistently. Newspaper and magazine ads can be targeted, but you still can't ensure the right people see them. 

A well formed direct mail campaign can guarantee that you reach the right people with the right message. For even the most basic direct mail campaign, you need to consider the frequency between when the prices are sent. The number of pieces to be sent also varies based on the product or service. Too many, too quickly, and the prospects will be turned off by the campaign. Too few pieces or not frequently enough and the prospects won't remember and connect the materials. Other considerations include the choice of using a predefined series of pieces or sending multiple stand-alone pieces. 

These don't include the considerations relating the how the market is defined, the size of the market, the complementing marketing techniques used, or the design and message on the pieces. Each campaign develops through a process. While there is no way to define the "best" campaign, there are some basic rules that a campaign must follow to have any chance of success.

1. Use a list of 500 or more prospects for a valid statistical test.
2. Send at least three pieces to each prospect.
3. When possible, create three unique pieces or a series of materials.
4. Incorporate a tracking mechanism for each mailing sent or various pieces.

There are many other options or variations that can be included in direct mail campaigns. Each option or variation adds complexity to the campaign and must be chosen carefully. Initial direct mail campaigns should focus on the basic campaign rules defined above.

Beyond the considerations above, a campaign must adhere to all regulations and rules of the US Postal Service. These define the regulations as simple as the height vs. width and thickness. More complex regulations include encoding address and mailing data into an Intelligent Mail Barcode. Other sorting, tray requirements, weighing, and documentation requirements must also fall within the guidelines.