Re: what days are cheaper
fraudia bhai generally speaking tues, wed, and saturday are considered to be cheaper days to fly. Fri, Mon and Sunday are a lot more expensive. That said, the market or route that you are traveling could also effect that. For example, in domestic US and Canada routes, this rule works more strictly as opposed to international flights.
I am sure you already know that travel agents usually buy blocks of seats at cheaper fares, and then resell them to retail customers at a premium price. So having some connections with travel agents may also help, specially for international flights.
One piece of advice: try to travel on jetblue or southwest, as they don't charge hundred plus dollars to change flights like other US/canadian airlines do.