Here are some questions to ask when planning your new superheroic campaign:
It can be helpful to establish the tone of your game by creating one or two campaign aspects, such as Mutant hysteria or Who watches the watchmen?. You can also use some optional rules, like Genre Stunts, to encourage a style of play. Some games will feature knock-down, drag-out fights through downtown, while others are about supers being hunted by the government or alien invaders, and you can use aspects and stunts to get your group in the right mindset.
You can use campaign planning aids, like A Spark in Fate Core, to help make group decisions about the feel of your campaign.