One of the most important aspects of direct marketing centers on choosing the right demographics.  Although we will be covering this much more in depth, the following are some universal demographics which can be looked at from the beginning.

By Geographic areas
a.    By State, County, Censustrack, MSA, area code, zipcode, etc. 
b.    International, by Country or further

By Product type to be marketed
a.    A product can generally provide a demographic “map” to the right customer.   An Xbox could be marketed successfully to a younger group, while Xlax should be marketed to the reverse.

By Brand
a.    In Mortgage, that would be by investor, in retail by manufacturer

By Customer Analysis - Who are your current customers, and what specific information do you know about them?   By analyzing you current customer base, you can increase your market share across those groups.  However, remember that this can be a trap.  Often, the best marketing programs focus on those prospective customers that you are not currently attracting, and thus opening up a whole new market.
a.    Loyalty
b.    LTV – (Not Mortgage LTV) – Lifetime Value of the Customer
c.    RFM (Recency, Frequency, Monetary Analysis) – commonly used in data mining
d.    Modeling to Predict Sales and Behavior

5.    By Industry Specific Demographic Profile – i.e. Credit score in Mortgage, etc.