Practice practice practice. Listening to a foreign language isn't something you can cram the night before in a few hours of revision and ace like other subjects. Surround yourself with French in the form of past papers, cartoons on youtube, French music, change your phone settings to French (this one sounds silly but since people tend to go on their phone so much and can navigate it without reading what it says because we know it so well it helps with your understanding of sentence structure and vocabulary, mine is in French and it helps me out alot and sometimes I talk to siri in French too) and even making a French friend if you can (I have one who I Skype with as I help her out with English and vice versa)
On youtube, search 'Petit Potam' it's a little kids French cartoon and I watch it while doing my homework or just having it in the background while getting ready etc just to familiarize myself with the accents and language, which does subconsciously work as it is part of the way we learn our native tongue.
For past papers, download the transcript of it (this should be on the exam boards site) so you can piece together what you're reading with what is being said and it will develop your understanding, do this until you feel comfortable to take away the transcript and listen to the past paper alone and it should help.
At the start of the exam, you should get 5 minutes to go through the paper, during this time I try and translate as much of the options on the page into French as possible, and if there are more than one way of saying it (for example: going shopping could be 'faire du shopping' or 'aller au magasins'
so I am able to match what I hear with what I'm reading incase I miss any of the sentence or just don't have time try and think about what has been said, it's easier to see what I've written and think 'ah yes that must be it'
Hope this helped