From the wiki: "Each player can place a single figure in reserve while deploying. This miniature is placed after his opponent’s initial deployment (If placing first) or after the opponent has placed their reserve miniature (If placing second)."
http://infinitythegame.wikispot.org/Deployment_and_Initiative
So basically you leave one guy and see how your opponent deployed than you put that guy accordingly. It might be interesting to pick something with Infiltration or Mechanized Deployment also I had fun with this and mines. There is quite a bit of things you can do this way. I hope this helps.
edit: and ninjad by CDK.