The trick to do nohup and be able to enter username and passwd etc. is to go into C-Shell, csh. I usually use an advanced C-Shell called "tcsh". This is the exact steps:
$ tcsh $ cd <to the directory>(Where the startWebLogic.sh locates) $ nohup ./startWebLogic.sh
<enter user name and passwd if asked> <Press Ctrl-Z to suspend it after all the starting messages have been displayed>