The JLPT is something nice to put on your résumé, if nothing else. It’s an officially accredited test of your Japanese proficiency.
For listening, practice practice practice. There’s a few practice questions on the official website at http://www.jlpt.jp/e/samples/forlearners.html – or you can ask Google-sensei.
One sneaky trick with the listening questions is that all of the multiple-choice answers will be spoken in the recording, to prevent you from just cherry-picking specific words out of the passage. For example, if the question is, say “at what time did they agree to meet?” with the given options as 8:30, 8:45, 9:00 and 9:15, then the recording will go something like “How about we meet at 8:30?” “No, that’s too early – how about 9:00?” “I have a meeting at 9:15, so I can’t do that.” “Guess it’ll have to be 8:45″. Or something like that.