Narrative Collaboration
Idea Farm
Plan for a few checkpoints throughout the campaign where you touch base with your players to get their ideas. The most crucial comes at the start of the game. It's best to take this step before you even set to work on crafting the world or plot, so that player input can define what's important in the game world. Later, checkpoints can coincide with major story milestones. For example, if the players launch their starship into space, you might ask where they want their voyage to end and what planets, if any, they'd like to explore along the way.
Creative Collaboration
Your collaboration will depend on the interests of you and the other players. Maybe one draws a city map, another makes the stats and personality for an NPC, another controls some monsters in combat, and a fourth doesn't want to do anything beyond playing their character. There's a trade-off here, because while you'll be off-loading some of your work, you'll also need to ensure consistency across these multiple sources of ideas. It can really help to keep a log of which player is in charge of each part of your setting. If you expect one of a player's specialties to appear in an upcoming session, let them know ahead of time so they can prepare or discuss their ideas in advance with you.
Decentralized Storytelling
This approach works best when players are comfortable with one another and willing to both take responsibility in building the story and accept that some of their ideas will go unused. It's well suited for shorter campaigns, or ones in which players take turns in the GM's seat.
Challenges
Shared narrative control also complicates planning ahead. The group might need to improvise an encounter, take a break while you (and maybe other players) prep to go in a new direction, or even revise their plans. It helps to limit yourself to creatures that you can quickly find stats for in Alien Core or another monster book to avoid spending hours of work on creatures you won't use.
Also, don't lose sight of your own enjoyment! You shouldn't sacrifice how much fun you have for others.