A clothing company is launching a baseball kit line and wants to advertise their video ads within baseball game inventory. Before setting up their campaign in Campaign Manager 360, what's the first thing that they should do?

Before setting up a campaign in Campaign Manager 360, the most crucial first step is to confirm publisher requirements for specific campaign dimensions. This ensures that the video ads will be compatible with the inventory available on baseball game sites, preventing technical issues and wasted effort later. Adjusting file sizes or creating companion banners are subsequent steps, necessary only after understanding the publisher's specifications. Sending video ad tags to publishers is the final step in the trafficking process, not the initial planning phase.