Maintaining a Clean Database
Databases are the most useful tool in your business as they form the direct source of your marketing. A well maintained and detailed database can be invaluable as it can make sure your marketing is targeted to people who firstly, actually want communication with you and secondly, are likely to buy as a result.
For example, if I am a owner of a book store and I have stored in the database customer details and purchases I can use this information to my advantage. If a customer has bought the first book in a series if I target them every time a subsequent title comes out I'm likely to get a high percentage of sales as a result versus a similar campaign to the general public.
This makes maintaining your database your biggest priority but it often gets put to the bottom of the pile as mere administration work. Make sure you make it part of your weekly activity to work towards contacting everyone in your database over a period of time and to keep it updated and effective.