If you're referring to casual conversation in English, here are a few phrases I use when speaking to friends, not really polite:
Instead of Hello, we use a more casual word "Hey"
We also use the phrase "What's up?" or "Sup" Which means what is happening with you or what are you doing.
Also useful phrases in general are found on this website. http://www.speakenglish.co.uk/phrases/more_common_expressions