It’s generally more expensive to depart on a Friday, if you have to leave on this day you can still search on Cheapflights to find great options that meet your needs.
Due to multiple factors, expect to potentially pay more when booking in December. For low rates, September can be a great choice for travel to Queretaro. Flights to Queretaro from Newark in September are about $474 on average during September, but can be found for as low as $178.
When flying from Newark to Queretaro, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.