Speaking French like a French would...and understanding when a French person answers back.
I've been learning French for some time now, and I think one of my greatest concerns is that even in knowing the grammar rules and vocabulary, I still get tied up when listening to spoken French. Apart from literal comprehension of what is being said, I also have trouble when French slang is used. It'd be great if Duolingo provided resources to connect actual formal "perfect" French with the French that actual French people speak. It's just a thought, I understand that Duolingo is a yet growing resource, and I appreciate it nonetheless.
Also, can anybody provide tips on improving my comprehension of spoken French? It's not that great at all...I REALLY wanna be fluent in the language...REALLY.
How about watching subtitled movies or TV shows? If you can, use french subtitles, so that you can see the words you're hearing.
Easy answer: listen to french! Try some conversation classes (online ones are available), watch tv shows and movies like Yusei said and listen to music, audio learning like Michele Thomas and Pimsleur are great for me but they are a costly resource. In my opinion the only way you can get fluent is to engage with the language and you can't really do that on a computer, you need to find french people or speakers and use the language in real contexts.