Just listen a lot! Try listening to the same thing intensively over and over. I know some people try to write everything down until they feel they’ve heard every word clearly. Find a Japanese band you don’t mind listening to over and over.
Been in the hook with Japanese music lately… Makoto Kawamoto, DAOKO, frederic, Perfume, SCANDAL, BABYMETAL, BAND-MAID, RADWIMPS, and anime music in particular. It helps quite a lot actually, was able to observe some things. Although I feel I still need more exposure.
Try podcasts? I’ve recently come across Nihongo Con Teppei. It’s a podcast by a native Japanese man, spoken all in Japanese at normal speed, about random everyday topics. It’s interesting, and not at all like listening to a textbook’s CD. He does an intermediate level podcast (which is absolutely awesome) and a beginner podcast (which I haven’t listened to as I think it might be too easy for my level, that said, because of who it’s by, I bet it’s great too). Each podcast is 15 minutes long, so doesn’t take a huge chunck of time or concentration, but the repeated exposure has helped me to really listen along and reinforce grammar principles. I can’t recommend this guy enough tbh.
I really like listening to lots of Japanese music too.
You’ve mentioned some bands, here are some other good ones off the top of my head…
Gen Hoshino
Masaki Suda
Kenshi Yonezu
レミオロメン
Scott and Rivers (It’s literally the guys that did Weezer, but in Japanese! Omg)
I was just about to mention Nihongo con Teppei - I listen to the beginner podcasts from time to time (about 5 minutes per episode) and really enjoy them.
Lots and lots of practice. And then practice some more. It’s also good to use materials that either have Japanese subtitles or at least some form of a transcript so that you can gauge the accuracy of your listening so you know where you are weakest and possibly not hearing things correctly. I like to listen and then write down what I think is being said and then go back and double check my transcription versus the subtitle script/official transcript.
I also recommend Nihongo con Teppei, I have not checked out the beginner podcast by him but give it a shot.
I find it nice to listen to a film or a series over and over and over and over, make it the BGM of you life for a month or more. For me it helped to already know the story beforehand so that you can focus on listening to the language, find patterns and notice frequently used vocab rather than understanding the meaning of the story. If you have a series or film that you love love love and could listen to A LOT then try it out.