Examples:
I'm sick of following my dreams. I'm just going to ask them where they're goin', and hook up with them later.
-Mitch Hedberg
The jazz boom was goin' on then so there was a lot happenin' in New York at that time.
-Mose Allison
The first speaker left out the -g in the second going, but not in the first. Why? When would a native English speaker omit it and when not?
(I'm interested in both oral and written form. But I guess the written omission is just to represent the former?)