Typically weekdays have better fares. Fridays and Saturdays are usually more expensive versus a Tuesday or Wednesday. Please keep in mind that is based on availability so it is always best to check one day before and after the dates you are checking.
Advance purchase is also important, the more in advance you purchase the ticket the lower the fare will be. Airlines usually have advance purchases of 3, 7, 14, and 21 days. Don’t procrastinate, book early. Always look in advance. Airlines tend to charge more money as the date of departure arrives. Keeping that in mind it is not a good idea to purchase your tickets before your plans for travel are finalized and your dates are confirmed because most airlines will charge you penalty fees to make changes to the airline tickets.