I’ve dabbled a bit in the past, but this year I'm serious about learning, so I'm attending a class: Māori language for beginners Te Ara Reo Māori (He Pī ka Pao). Astonishingly, this 36 week course is free from Te Wānanga o Aotearoa.
To help me learn vocabulary I've turned to flashcards and am finding the free open source app called Anki extremely useful and effective.
So far my biggest annoyance with it, apart from its clunky look, is having to type words with a macron in another app and paste them in:
The toolkit Anki is built on has trouble dealing with a few input methods, such as holding down keys to select accented characters on Mac OS X …
One source of handy info for using Anki is Fluent Forever. The manual is also quite well written.