According to the Law of the People's Republic of China Concerning the Administration of Foreigners Entering and Leaving the Country, foreign tourists must apply for visas at China's foreign affairs offices, consulates or other organizations authorized by the Ministry of Foreign Affairs. A group of five tourists or more can apply for a group tourist visa. This is usually handled by a travel agency organizing groups. People coming to China from countries which have visa agreements with China (such as agreements which exempt tourist groups from visas) are treated in accordance with these agreements.

If you want to go to Tibet for a visit you can apply for a visa only with the consent of the Tourism Administration of the Tibet Autonomous Region or any one of its foreign representative offices. A passport is required for visa application, the passport shall be valid for at least 6 months beyond the duration of the tour.
Visa is required for Canadians, Americans and people of most other nationalities who travel to China. You can apply it directly at the Chinese Embassies and Consulate Generals around the world:
For Canadian and US passport holders, visa is not required for Hong Kong if your stay is less than 90 days as a tourist. For other passport holders, please consult with your nearest PRC embassy or consulate.

CANADA

U.S.A.