General > Rocket Languages Blog) suggestion number 4 is to "Sing at the top of your lungs." Of course lyrics need to be learned first and my favorite way to learn them is with lyric videos on YouTube.
Here's one I recently found:
二時間だけのバカンス featuring 椎名林檎 宇多田 ヒカル
[Nijikan Dake no Vacance featuring Sheena Ringo | Utada Hikaru]
カラオケ: かな＋漢字 + ふりがな
karaoke: kana + kanji with furigana
eta: YT removed the video :-(
If you find a Japanese song with lyrics to sing along to, please share.
(If YT says a video is not available in your country when you follow a link, try doing a search. Sometimes there are mirrors.)