Formal:
* நீ என்ன பண்ணுறீங்க? (Nee enna pannureenga?) - This is a polite and formal way to ask, suitable for elders or someone you don't know well.
* நீங்க என்ன செய்றீங்க? (Neenga enna seireenga?) - This is another polite and formal option, also suitable for elders or someone you don't know well.
Informal:
* நீ என்ன பண்ற? (Nee enna pannra?) - This is a casual and informal way to ask, suitable for friends or family.
* என்ன பண்ற? (Enna pannra?) - This is a very casual and informal way to ask, suitable for close friends or family.
More specific meanings:
* நீங்க இப்போ என்ன பண்ணுறீங்க? (Neenga ippo enna pannureenga?) - What are you doing *now*? (formal)
* என்ன பண்ணிட்டு இருக்க? (Enna panniittu irukka?) - What are you doing *right now*? (informal)
The best choice for you depends on the situation and who you're talking to.