I find that if I list at least 48 hours in advance and round trip, I don't get selected. Anytime I list within that 48 hour window or one way, I am chosen. I started looking for patterns when I realized that 4 trips in a row I was selected and that just seemed beyond random. I actually prefer to be chosen because I get through security much faster in most airports. In fact, I got the the last seat on a flight out of MCO in November because I was chosen and someone missed their flight due to long security lines (flight was oversold by 7 when I checked) so I don't mind.