Was taught/had lessons for:
...But can't remember much of either language.
Actually know/can speak:
(I'm half English, half Polish, so learned from my parents and being in the respective countries)
Just goes to show that real world experience > learning to read/write in terms of actually picking up a language. I remember very little French/German unfortunately.
I'd like to learn some new languages at some point. I'd especially like to learn Mandarin and Spanish because of the huge amount of people that use both languages. I feel they'd be useful to know. I also want to give German another go just because I love the language.
To answer your questions:
Why I learned: Because I had family in Poland and so visited the country fairly regularly, and my mum spoke to me in Polish a lot, so I picked it up.
In school I was obligated to learn French and German. It went terribly, I remember very little.
As for tips for learning languages: TALK! As I've said, learning to read/write the language or learning the language theory is a poor way to learn a language. I learned much better from simply being in Poland and attempting to speak with my broken Polish than I did in my French/German classes. Another good thing is to absorb media. A great one is subtitles. Watch movies with English subtitles, or watch movies in English but with subtitles in the language you're trying to learn. Or play video games in that language. Best is just to socialise with people from that country and speak the language though.