Okay, because I was a linguistics major in a previous life, my sister is now asking me for guidance on learning languages. But linguistics is just the study of language itself, not specific languages; and, though I have studied eight or ten languages over the years, I haven't been particularly good at learning them.
So what has worked for you? Immersion is out: I'm aware that it helps lots of people, but my sister lacks both the money and the mobility to do that. She does have access to a computer, and I believe she has a little money, but not much, so free or low-cost suggestions would be especially welcome.
Different things work for different people, so I realize that some method that worked great for you might not work for someone else--but just hearing about stuff (commercial courses, self-study tricks, computer services, whatever) that worked for *somebody* would be really helpful. I'd like to give Sis a bunch of different suggestions if I can.