Choose the day you travel
My guess is to try to travel on a tuesday or wednesday, it won't increase your chances of being upgraded but it is possible that standard class will be half empty. I have no evidence that these 2 days are quieter but is logical. Most people start or end their holidays at the weekend. With business travel there is this thing about using the weekend or work day to travel, my guess is that most business travel is on sunday, monday or friday,saturday.
Give me half empty standard than an upgrade on a busy flight