Learn the "four tones" of Mandarin as much as you can. There are many resources on the web that tell about the four tones. Search Google for "tones of Mandarin Chinese". These are the basics of Mandarin pronunciation. Do not be too concerned if you cannot get it right, it can be very hard. A bit of "foreign" tone makes you sound interesting, and are what set you apart from a silly foreigner trying to speak Chinese and a fluent Chinese speaker. Learn to say "Ni Hao". "Ni Hao" literally translates into "You Good" and can be a very generic greeting term. It is pronounced like "nee how". You can say it when you shake hands with your Chinese friends, when you walk by them in the hallway, when you sit down next to a new friend at dinner, etc.etc. It can be loosely used in all situations where you may say "hi" or "hello" in American English. Learn to say "Xie Xie". "Xie Xie" means "Thank you". It is pronounced like "Shi-e Shi-e" or "Zhi-Zhi"(if that is not too confusing). It can be used whenever you want to say thank you to someone.
Belinda