One of the things I could talk and write more about is the fact that English is my second language (technically speaking, it's my third language because I've grown up bilingually with Bulgarian and German). I don't claim my English skills to be at the level of a native, but I do feel very comfortable speaking and writing it, so I thought I might share a few things I've found helpful for practicing a foreign language over the years.
Any foreign language, independent of your age, should be started with a course with a dedicated teacher, in my opinion. It keeps the motivation level high over time, it works as an accountability partner, and it's also very important for laying the foundation of knowledge properly. Once you have overcome the beginner's level (A1), I have found the following ways to include the new foreing language in my daily life and start "thinking" in it very helpful:
Films and Series
Start by watching films and/or series that you have watched before, but this time around watch them in Spanish, French etc. with the corresponding subtitles. It will give you the opportunity to follow the story in the forein language without the pressure and frustration of missing something because you already know what happens. Most streaming services don't offer a wide variety of alternative languages, so my top tips would be to borrow DVDs from the library, or digital versions on iTunes etc. This is one of the best ways to start getting comfortable speaking the new language, apart from the actual speaking of course.
Another, seemingly obvious, way to practice the new language is to read in it. When you are starting out as a beginner I would recommend the library and bookshops for level-specific literature. Many of them also have little "vocabulary boxes" on the side of the pages with translated words. Once you're more advanced, I recommend reading books in their "original" language if it's, for example, by a Spanish native author and you are trying to practice and improve your Spanish. Also, actively seeking out native authors of that language is such a good way to read and get to know different voices, whether it's the actual voice of the writing, or the cultural voice.
There are also specific magazines for learners with articles in all levels. For example, when I tried to practice and improve my Spanish skills, I subscribed to the monthly magazine ECOS by the German "Spotlight" publishing house. Spotlight offers many great ways to learn Spanish, if you are a German native speaker because all vocabulary boxes translate Spanish to German. It might be worthwhile to do a little research for a magazine or podcast that offers this type of learning in your native language.
For short and easy ways to include the new language in your life, listen to songs written and sung in that language and seek out some YouTube interviews with your favorite actors, musicians, or authors where the interview is dubbed in that language. It makes for a fun and easy way to learn the colloquial and informal ins and outs of the spoken word.
I have been told that there are also apps for learning new languages, and if you are at an advanced level, I would also recommend seeking out podcasts in your language of choice.
In general, try to make it as fun and easy on yourself as possible. When we are in school we "have to" learn and study so many things, that it can raise significant resistance to learning new things later on in life, after you have studies for 12+ years already. And there are so many things we "have to" do and are responsible for as adults in our lives that "having to" learn a new language often feels like just another to-do that gets shoved down the list so low that we never get around to doing it.
But it doesn't have to be like that. It is never too late to start a new habit, or learn a new skill, and if you can do it on your own time and in your own pace then there is a golden opportunity to make an adventure out of it on a daily basis and share it with your loved ones, be it with movie nights or dancing to music. Every little bit counts and adds up to your knowledge of that language.