Originally Posted by Geezer57
3) Try not to give kill orders to any of your assassins against visible rival agents (Emmisaries, Princesses, etc.) within the same friendly port or border province. Should that target agent choose to depart for a hostile foreign port or border province (one with a BF or rival agent) during the action phase, your agent will follow them and risk death. Instead use an assassin(s) from an adjacent interior province, first move them from home province to target province, and then jump them on the rival agent (giving the kill order) in the same turn. Your agent will move and attack after you hit the END YEAR button, but won't leave the target province until the next year - giving you the chance to review their new target province (if their target has left).
I like to eventually end up with multiple assassins/spies in each of my provinces, but ports are especially valuable as "agent traps" against the AI.