Make sure you use the Create a New Custom Report, choose the folder: Other, and look for a Report Type that already has the Objects you are looking for.  HOC has populated the Category: Other with many common report types.  If, however, it is not there, we will learn how to create one from scratch!

Go to Setup / App Setup / Create / Customize Report Type.  You will be given a welcome screen there with general information about this process.  It is always good to read this information.  Hit Continue.

What do you want the rows (details) of the report to focus on?  What is your primary goal of this report?  This first dropbox allows you to set the primary object and from there, you can bring in other related objects.  With this example, we want to find out how different contacts answered our opportunity questions for different occurrences.  Our primary, in this case is Occurrences.

It is a good idea to name your report type with the objects that you plan to have associated.  In this case, It is going to be Occurrences, Connections, and Answers.  Make sure to tab through to the next box, and HOC will auto-populate it for you.

Give the Report Type a description.  Clear and concise.

Store your new Report Type in the Other Reports Folder.  (At this time, we do not have the option of creating a new Report Type Folder).  By putting the report Type in this Other Reports Folder, you will always know to go to that folder to see HOC or you have created what you need.

You can choose, at this point, to publish or keep this Report Type in Development.  I know that I am about to use this report, so I am going to choose "Deployed" and hit Next.

HOC gives you a visual representation of your data structure in this window.  These are called JOINS, where you are joining one object with another.  You are finding information that is common in all the objects you are choosing. The dropbox shows you related Objects that you can bring in to this report.  Our next Object is Connections

You have two options.  The first option is to pull in data that is contained in both A and B (see the visual representation to the right).  This is called an INNER JOIN.  In basic language this says:  Pull in information only when it is part of both A and B.  

The second option is called a LEFT OUTER JOIN.  In basic language this says:  Bring in information about A and B, even if there is no information in B.  See the grayed circle and note the data below it.  Some of the A records do not have B data.  In our report, we only want data that is in both sets, so I am going to change it back to an INNER JOIN.

We need to bring in the Answers associated with these connections, so I click box below B and add another related Object.  I choose Answers and I want another INNER JOIN.  What does this say?  Bring in Occurrence information when there is a Connection and that Connection has Answers... Note both the venn diagram and the data structure below it.  

Hit Save

Assuming you chose to Deploy your report type, you can now find your new Report Type in the folder: Other Reports in the Build a New Custom Report Window.  Even my Description appeared!

Navigate back to Setup / App Setup / Create / Report Type and choose the ALL view.  You should see your report listed.  Use the edit button to change the joins, description, or related objects.

For more information on Custom Report Types, see: SF Help & Training: Custom Report Types.