"Hello. Whats up?" in Spanish
It changes from country to country. In Spain hola, ¿qué pasa?, in Mexico, ¿Que onda? in Argentina ¿Que haces? (pronounced hacés), etc,...
this are words that are used more often by teens.
?que tranza? (what's up?)
?que hondas vato? or more comon ?Que honda guey? (what's up dog?)
What i hear usually, is Hola que haces, which is actually "what're you doing?", but it's more common.