How to restore a dump file with the Oracle SHOW=Y option

We often receive dump files from clients to develop applications and provide support for those applications, and often we have problems restoring those dump files. If we know a user where we can restore the database using "from user, to user" switch then the process becomes easier after several attempts while identifying the user or roles missing.

The process seems to become impossible when the customer does not know a user to use for a restore and we try to do a full restore. One issue I run into is that there is a different file structure at which the import fails. Another problem is not knowing objects that need to be precreated, and also, the full restore seems to overwrite the password of default DBA accounts, making the database inaccessible.

There must be a better way. What do you recommend? Must we require specific information or can you give us a list of specific steps and commands that will ensure a good restore?

 imp file=my_dump.dmp show=y log=import_show.txt full=y