Try to set aside some time to regularly practice speaking. You can find a language partner here on italki. It can also be useful to watch TV series or movies and listen to pop songs to get your ear more accustomed to hearing Mandarin. Mastering pinyin can also help you to understand how to pronounce Mandarin words and it is useful for typing or sending text messages. One final note, Mandarin does not have a regular alphabet. Words are based on visual symbols rather than on phonemes that represent sounds. There is a teaching alphabet used in elementary school to help master the sounds called bo-po-mo-fo. Here is some more info about it, and a chart of how to pronounce EVERY Mandarin syllable. http://www.mandarinbook.net/bopomofo/

Mint, those are very good advices, thanks. i will always remember them I do speak xie xie and ni hao with my friend sometimes, my friend's chinese but she cant speak mandarin. So when I saw Italki website I agreed to join it. The result? I found it is a good place to communicate with people from the whole world.

You can speak "ni hao"你好 "xie xie"谢谢, zai jian 再见。some simple. Even I am native mandarin speaker, I forget a lot of pin yin and characters If I didn't use it. For english, I am keeping still in improvement. I need to know how to speak it well too.

To imitate the pronounciation.