Greetings and Politeness:

Hello – 你好 (Nǐ hǎo)
Thank you – 谢谢 (Xièxiè)
You’re welcome – 不客气 (Bù kèqì)
Please – 请 (Qǐng)
Excuse me / Sorry – 对不起 (Duìbuqǐ)
Goodbye – 再见 (Zàijiàn)