The way that you store your SQL data -- files, lookup tables, databases -- is important. For example, even though SQL Server databases can store multiple tables in a single Database file, you usually don't want to store all of your tables in the same Database file. This is because tables used by two or more databases will require you to open the entire database and tie up resources that are better used for other purposes. And you certainly don't want to have a proliferation of files simply because they serve two or more databases.
How you organize your data, and in what files you store them not only affects SQL Server's consumption of server resources, but it also impacts the data that needs to get backed up. Why should you continually back up a lookup file where the data rarely changes? Separating the transactional data in an application into their own database files while you move more static lookup tables, such as tax tables, into utility files lets you set a much more reasonable backup schedule, and can often dramatically cut down on your need for additional backup resources and narrow your backup windows.
Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics.