Localisation: English and Chinese

Hi,

I’m wondering what the best way is to approach a multi-lingual install of WordPress?

I have a theme and am aware of some tutorials out there to create .mo files for various languages for strings of text.

However what I’m not aware of is how to switch between the languages?

I want to have 2 flags, one for English version and one for Chinese and when the use clicks one the language changes.

Any ideas on how to achieve this?

Thanks