In general, if the business entities are modeled correctly in a logical model and assuming the database will be normalized, most of the entities in the logical model will eventually become tables in the database and the attributes for a given entity become columns in the respective table

However, in many cases the DB architect or the development team might decide to de-normalize the data in the database (for performance/technical reasons).  In these cases there could be multiple tables in the database which contain information about a business entity.

- Adrian

Here are a couple of resources on creating E-R diagrams:

Data Modeling: Finding the Perfect Fit

Logical Data Structures (LDSs) - Getting started

Introduction to Data Modeling

Just Enough Structured Analysis - see Chapter 12

Depending on what tools you have at your disposal, using a class diagram to model data is also an option - here are some articles on class diagrams.

- Adrian