Where can I find cheap flights to canada or america from the UK?

I am flexible on dates, and don't mind where in canada and america I go to.

I don't mind where in the UK i fly from but would prefer Manchester, Birmingham or Liverpool though I would be willing to travel to any airport.Where can I find cheap flights to canada or america from the UK?
Buy well in advance, travel on weekdays, stay over one Saturday. Use the online flight sellers to find your flight and expect to change planes. Avoid high travel seasons. Also avoid winter, unless you're willing to tough out the weather. Another tip, for the USA, book though southern cites in cold weather, and northern cities in warm weather. Also, book you departure for afternoon so the security line is short. Return book flight toward evening, so you can immediately go to bed once you get home.Where can I find cheap flights to canada or america from the UK?
Please check:

Tips:

a- use flexible dates

b- use alternative airports



http://www.hotwire.com/



http://www.cheapoair.com/



http://www.kayak.com/



http://www.orbitz.com/



http://www.priceline.com/



http://www.expedia.com/default.asp



http://www.farecompare.com/



http://www.bing.com/travel/



http://www.airfarewatchdog.com/



http://www.cheapair.com/