Navigate to Setup->Create->Report Types

Click the New Custom Report Type button

Choose your Primary Object. This is going to be the controlling object in the report. All other objects that you want to include in this report will need to be related to your Primary Object. Also, give the report type a Label. This should be descriptive and include the objects in the report so that you can reference it later. Also provide a Description, choose a Category in which to store the report, and select Deployed if you are ready to use this report type in your production.

Click Next

Click to relate another object (if you want a second or third object in your report)

Choose the Object of your choice from the list

Choose if you want each record of the primary object to have at least one related secondary record. (Example: Campaigns WITH Campaign Members)

OR - if you don't mind if your primary object has or does not have a related secondary record. (Example: Opportunities AND Household) This is sometimes referred to as WITH OR WITHOUT.

Repeat to add a third object (if you wish). Click Save.

You are finished! Now, follow these instructions to create a new report and select the report type you just created:

http://kell.screenstepslive.com/s/knowledgebase/m/16056/l/169541-how-to-create-a-new-report