You can package multiple portlets within a common, single, portlet applicatio war file. These portlets can share information through the Application Scope of the PortletSession. Check out my signature links for some free tutorials on the subject.
However, JSR168 portlets don't really call each other. There's no mechanism to do that, and it's not really how portlets are intended to work. Portlets are supposed to be independent creatures sharing space on a portal page.
What you might need is a
JSF portlet that allows a wizard like experience through a portlet. It's a very proven
pattern.
Also, IBM provides things like C2A, click-2-action, to provide inter-portlet communication. They also provide a PortletService framework to perhaps facilitate sharing information. IBM specific though, so don't bet the interoperabiliy of your portlets on it.
Keep asking questions - we'll get you thinking like a portlet developer in no time!
-Cameron McKenzie