Asking about action:
What are you doing at the moment?
Lagi ngapain?
Right now I'm reading this.
Lagi baca ini.
Asking about the quality of something:
How is it?
Gimana? / Gimana rasanya?
It's pretty good.
Lumayan bagus. / Lumayan enak.
Asking someone to describe something:
What is it like?
Gimana bentuknya? / Kayak apa?
It's very useful - and interesting.
Berguna banget - dan menarik.
Asking about the condition of the action:
How's it going?
Gimana kabarnya? / Gimana jalan ceritanya?
It's going well.
Lancar.
Asking about progress towards a goal:
How are you getting on?
Gimana perkembangannya?
I've only just started.
Baru mulai.
I've almost finished.
Hampir selesai.
Asking about someone's progress towards achieving or finishing a task:
How is your learning Bahasa Indonesia coming along?
Gimana belajar Bahasa Indonesianya?
It's coming along well.
Lancar.
Asking about someone's impression of (especially) a new experience:
How are you finding it?
Gimana menurutmu? / Gimana rasanya?
I'm finding it a bit difficult - but it's interesting.
Agak susah sih - tapi menarik.