The phrase "How are you" has evolved into "How is it going," "How's it going," "What is up" (with an optional "homie g" at the end), "What's up," and "sup." "Sup" has become a general greeting, much like "hi" or "hello." Because "sup" produces the undesirable "s" and "p" sounds, the betterway of saying "How are you" is "zab."
Person 1: hi
Person 2: zab, yo
Person 1: nm. i had an amazing daytoday.