This is my personal favorite day. Today, you get to pick a song you like in your target language and learn any words in it you don't know. This just means that next time you listen to the song, you should be able to understand mostly all of it. Pretty cool?
Ideally, you would find an online version of the song with lyrics and a translation, such as the following video for a Hindi song.
Even if you can't find a video on Youtube with both the lyrics and translation, it's still likely that you can find the translation on some website. I strongly recommend finding both a source of the lyrics and one for the translation since often in music, the grammar or vocabulary is not what is commonly spoken, making it difficult to directly translate without the guidance of the translation.
Using whichever flashcard system you want, take note of all the words you do not know already so you can learn them. Not only will you learn a lot of words, but these words will be meaningful to you, so even easier to remember. The more you are interested in something, the more likely you are to remember it. Use this trick to quickly learn a lot of vocab and boost your level.
As for different focuses depending on your level, there is not much I have to say since learning vocabulary through song is something you can do regardless of your level. So here are just some tips depending on your level.
As a word of warning, this technique of picking out new words in songs works best you already know some words and basic grammatical structures in a language, otherwise it becomes too overwhelming. So if you are an absolute beginner, I recommend first learning a bit more of the language before using this technique.
The first few songs you listen to will be almost overwhelming with vocabulary, mainly since songs often have vocabulary not used as commonly in everyday language. For instance, you will have an easier time finding songs about love than about asking for directions. So be patient and make sure you pick songs you really like.
Also try to find songs within the same genre, so that some of the vocabulary you learn in one an be used in the other one. There's only so many ways to talk about love! After learning the individual words from many different songs in the same genre, you will be more adept at picking out the meaning without having to look up each and every word in the dictionary.
Try to vary up the genre of songs you listen to. Maybe you reach a point where you only learn five words from a song (ideally the number should be between 15 and 30 depending on the song). This probably means you need to pick a song about a completely different topic. This way you will be exposed to completely new vocabulary and your learning will not stagger.