How does one come from Canada to the US and work? What type of visa is needed, and how long is it issued for?

Answer 1

i do know that Canadian do not need a visa to work in the USA , you will need an employer's letter about job descrisption and contract : here is what it says ;
Requirements for Canadian Citizens

Canadian citizens usually do not need a visa as a NAFTA Professional, although a visa can be issued to qualified TN visa applicants upon request. However, a Canadian residing in another country with a non-Canadian spouse and children would need a visa to enable the spouse and children to be able to apply for a visa to accompany or join the NAFTA Professional, as a TD visa holder. To apply for visa, please see the requirements under the section Mexican Citizens - Applying for a TN Visa - Required Documentation.

A Canadian citizen without a TN visa can apply at a U.S. port of entry with all of the following:

Request for admission under TN status to Department of Homeland Security, Customs and Border Protection, U.S. immigration officer;
Employment Letter - Evidence of professional employment. See Employment Letter below;
Proof of professional qualifications, such as transcripts of grades, licenses, certificates, degrees, and/or records of previous employment;
Proof of ability to meet applicable license requirements;
Proof of Canadian citizenship- Canadian citizens may present a passport, as visas are not required, or they may provide secondary evidence, such as a birth certificate. However, Canadian citizens traveling to the United States from outside the Western Hemisphere are required to present a valid passport at the port-of-entry;
Fee of U.S. $50

if you need more informations ?
here is the home page about working in the usa , with all the questions and answers :
http://travel.state.gov/visa/temp/types/types_1274.html

Answer 2

Working visa is needed for someone to work in USA from Canada.

Answer 3

The easiest way for Canadian citizens to work in the US is through NAFTA: no 'working visa' necessary. Here is all the information you need:
http://travel.state.gov/visa/temp/types/types_1274.html

Answer 4

uscis.gov has the various visa opportunities.