There are several possibilities. The simplest it to have users enable Advanced auto-complete in their Forms preferences. When they fill-in a different for, it will suggest values for them to use.
You can also make use of the Global object, but for it to work with more than one form they would have to disable the Global Object security policy in their JavaScript preferences, which is a security concern. Your forms could then use JavaScript to persist certain information in the Global object for later retrieval in other forms. Again, this is a security concern and should not be used to store potentially sensitive information.
Other less common methods include enabling the form to export form data and later importing it, which will work if the forms share the relevant field names, but this can only be enabled using LiveCycle Reader Extensions ($$$$$).
You can also set up a client/server system to store and retrieve information to/from a server, but this can be rather complicated and needs to be done with security being a primary design consideration.