Depends which stage I am.

If I am a beginner: read children's books, do extensive reading (reading while rarely looking anything up), learn as many words that I can, watch Youtube videos directed toward beginners so I can learn simple phrases and hear the spoken language, have conversations with speakers of my target language, read a grammar book and practice writing sentences as I learn new grammar rules.

If I am intermediate (meaning that I can have a conversation entirely in the target language on a limited range of topics and understand most of what is spoken to me): read newspapers and books (in subjects that I would normally read) alternating between extensive and intensive reading, listen to podcasts spoken entirely in the language every chance I get, watch TV shows in the target language (subtitles in the target language are okay), listen to music in the language, have conversations with speakers of my target language more frequently, use a grammar book only as an occasional reference guide, practice writing on a wide range of topics

If I am advanced (meaning that I can have a comfortably have a conversation entirely in the target language on a wide range of topics): pretty much the same as in intermediate level, only I make more of an effort to learn new vocabulary and avoid grammatical errors. Also, if possible, try to watch TV and movies with subtitles in the target language and understand all the grammar and vocabulary that the characters use. At the advanced level, I am more focused on perfecting what I have already developed.