I really want to learn Sindarin, but have not yet been successful. No idea how to go about it, really.
I've previously dabbled in Klingon, Tayledras - from Mercedes Lackey's 'Valdemar' novels - and recently Dothraki. My flatmates adore the televised version of Game of Thrones, which is how I was introduced to it, and though I wasn't a fan of the book I did appreciate how well thought-out the Dothraki language was. It's quite heavily inflected and the basic sentence structure is SVO, so as a Spanish student and native English speaker it wasn't a problem to pick up in terms of syntax. Unfortunately I didn't get far with it as I spent most of my summer revising the grammar of a real language instead.