I am bilingual in French (was born in France and lived there 25 years) and English (have lived in the US for the last 12 years). In my spare time, I study Spanish (advanced, learned it since middle school), Russian (intermediate, learned it on my own in college) and Swedish (beginner, learned it on my own this year). I guess it is a passion. It feels good when I use my brain to memorize and understand a different language. I also love discovering how people live in different cultures. I should mention I am on a 158 day streak on Duolingo (it could have been more but sometimes the changes they do to their app are so annoying that I stop using it for a while).
Every week, I set aside at least 1h30 per language. During that time, I warm up with a few lessons on Duolingo (15mn). Then I move on to Memrise (15mn). After that, I read a book in the language I am studying (30mn) and I finish with watching part of a movie or a tv show on Netflix (30mn). When I am done, I plan a half hour review a few days later to refresh my memory in between sessions. I am aware that I am missing the conversation part and it is in my plan to pay someone to converse with me. However, I agree with the previous posts in this thread, the best is to travel to a foreign country and talk to people (which is why I'll go to Sweden in a few months).
Everybody learns differently and to improve in a language, I believe it is necessary to figure out what works for you. I have some students (I am a French tutor) that have an exceptional memory and will remember everything we went over during the previous session. Others will only memorize what they hear, so we focus on songs, videos, talking, not so much reading and writing. The most important is to keep doing it on regular basis.