A notice by DM is sent to the company informing them that they are violating the patent usually stating that they are to cease and desist. If the company fails to contact and continues forward violating the patent without coming to an agreement, then DM will sue. There is a new tactic being taken by the violators to sue the patent holders first thus getting into a federal court that is either slow or favorable to them. Of course there is always the game of challenging the patent which can take years to review by the USPTO.