You actually flip a coin to determine who deploys infiltrators first. Then you alternate.
As per the rulebook.
I'll page number yo' ass later.
Dark Angels 1750 win/loss Record
Win - 23 (Belial helped wreck Ryan's puny Eldar)
Loss - 13 (Brice's Necrons wiped me)
Draw - 2 (The 13th hold out in alpha take and hold)