In our very first competition we made a concentrated effort in the last rounds to move up to 16th so we'd get picked into an alliance. We weren't.
Having watched a number of alliance selections, it's pretty obvious that most teams don't do much of a job of scouting or even have a plan. The alliance captain is up there stumbling around listening to numbers shouted from the crowd to make a choice instead of having a ranked list of teams to chose from.