I speak more than 8 languages. But that wasn't obvious at all from the start. My parents don't know any foreign language and my first contact with another language was at high school. Classes were not particularly effective either - how could they be, with 45 minutes of speaking time divided between 25 students and a teacher?! I got C's and D's mostly. Until I discovered the internet. I found that I really wanted to be able to talk to people from all around the world.
German (my native language) didn't get me very far. English helped me make friends in the UK, Canada, USA and even as far as Australia. It was tempting to stop there, but I noticed that most of my contacts still came from Western countries and I didn't hear many voices from poorer parts of the world. Learning French, I suddenly had more contacts in many parts of Africa and the Middle East, where French is the language of higher education. Spanish opened up South America for me. Esperanto gave me a lot of opportunities to travel (google my name and "How Esperanto changed my life" if curious). Chinese provided amazing insights, since they basically have their own internet, just as large as ours but with different trending topics, different petitions, right down to different memes. A whole new world at my fingertips. Besides, speaking English in China I was seen as a walking wallet, while speaking Chinese earned me real friends and an unforgettable trip.
I love languages, I just had to try them outside the classroom. Classrooms are boring, real life is fun.
MY TOP 3 TIPS FOR YOU:
1. Look for the fun. Too many people think that language-learning won't "stick" unless they're bored. The opposite is the case. If you're having fun hanging out with foreign friends or reading cartoons, that's when you'll learn a lot, because the brain is relaxed.
2. Aim to spend 10 minutes studying languages every day. If you're tired, just watch "funniest Spanish ads" or whatever on Youtube for your 10 minutes, sing along to a song or read a newspaper article online. If you're more awake, study a course or learn some vocabulary. To increase your chances of studying every day, find stuff to do while commuting, cleaning or on lunch break, for example listening to podcasts or using a mobile app. Variety is the spice of life (and learning). Whenever you managed to do 10 minutes of study, mark the day in your calendar and don't break the chain!
3. Use any opportunity to apply what you learned. As soon as you know how to say "Hello. How are you?", start using those words with restaurant staff or other local native speakers. You can also find language exchange partners online.
For more tips, google "LearnLangs" (my blog). There are also other polyglot blogs, Youtube channels and forums giving tips on how to learn languages. Before you invest in an expensive course, check out what kind of high-quality courses are available for free online. I'm creating such a website myself right now, it's called LearnYu and will teach Chinese. At this point, there are so many resources that you can learn any major language for free online.
I'll leave you with something to think about: "Languages cannot be taught, they can only be learned". Start learning!