My method is "write and pronounce". Writing words on paper leaves a visual memory trail of the words. If you just look words, you may forget them quickly, but writing them makes you concentrate on them more efficiently. Reading words aloud gives you a phonetic memory trail. It creates an echoing sound in my head and that sound I can recall later. When you know words enough, you will understand the principles of word formation in that language. This helps you guess meanings of unfamiliar words, when you read, and create word families in your memory.
Every day, I'd try to write down 10-50 words or phrases in French which I didn't understand, or words or phrases in English which I didn't know how to render in French. I'd go home and spend an hour or more looking them up in the dictionary.
I'd read newspapers, comic books, textbooks, advertisements, and novels.
I'd talk to teachers, fellow students, strangers at the bus stop, store clerks, etc.
By the way, I rarely watched TV, listened to the radio, watched movies, or listened to music in French... though this might just be a personal thing. I often have great difficulty understanding my native language, English, in recorded form. I still find recorded audio extremely difficult to understand in French, despite the fact that I can carry on largely fluent in-person conversations with native speakers.