Here are some common phrases for general conversation with people you already know.

Asking how someone is

?how are you
how's it going? (quite informal)
how are you doing? (quite informal
 
how's life? (quite informal
how are things? (quite informal
 
I'm fine, thanks
I'm OK, thanks
not too bad, thanks
alright, thanks
not so well
 
how about you
and you
and yourself

Asking what someone is or has been doing


what are you up to
 
what have you been up to
 
working a lot
studying a lot
I've been very busy
same as usual
not much or not a lot
 
I've just come back from 
Portugal


Asking where someone is