The internet makes it super easy to get a hold of music and media from pretty much every corner of the world with a click of a button, so take advantage of it! Find out what musicians, TV shows, and films are popular in the countries that speak the language you're trying to learn.
For instance, if you're trying to learn French, why not hit up Spotify to stream some Mylène Farmer, Serge Gainsbourg, or Christine and the Queens? Netflix has a great selection of French films like "Le Chef" and "Dans la maison" (among dozens of others) that could also be helpful. Whatever language you're trying to learn, do your research — there's plenty of free (and entertaining) help out there.
This isn't for beginners, of course, but once you move onto intermediate levels of the language in question, look for popular books by authors who are writing in their native tongue or translations of popular Western books (which could be extra helpful if you already know the general gist of the story). Write down words you don't know to look up later and you'll find that your vocabulary increases immensely the more you do this. It really will help take your skills to the next level.
You'll need a way to look up the words you saw in the books you were reading, and a dictionary is the easiest way to do it. I'm talking about a big, heavy, paper dictionary here — they're pretty readily available on Amazon, don't cost too much, and will be one of the most useful tools in your journey to learn a new language.
It'll also help to download a translation app. Google Translate is probably the most well-known and is also very easy to use. Pro tip: you can use the camera in the app to translate text on a menu or book directly. How cool, right?
It's not enough to know verb conjugations or which nouns are feminine or masculine. If you really want to be fluent in a language, it's important to learn the phrases that native speakers actually use.
Again, TV and movies are a great way to pick up on these (and if you watch with the closed-captions on, you can write them down to look up or remember for later), but you can also literally do a Google search with "[Language] idiomatic expressions" and find many resources.
Remember this from school? They're still helpful now. It's fine to see words in a foreign language on a screen, but it's a proven fact that writing things down helps us remember them. Just like you jot down words you don't know from the books you read, you should be making it a point to regularly spend time writing the language you're learning to speak.
Even though language-learning apps aren't my main way of learning languages, they're a fantastic supplement. As you get further along, the lessons offered on these programs might seem a little basic, but even more advanced speakers can always use a refresher of the basics. Even spending a couple of minutes a day on them could be helpful, so give them a try.