Step one is creating a digital home for all the essential info. Shared folders in Google Drive, Dropbox, or other cloud-based storage service will work fine, but we like Evernote (free), since it's made to organize many different kinds of media and present it in one streamlined package.
The comprehensive note-taking app for iOS, Android, Windows Phone, Desktop, and web gets your partner involved in the planning process with collaborative notebooks that let you and yours save inspirational photos, important documents, and notes to the same place. With shared notebooks, you both have access to contracts with vendors, travel itineraries, guest lists, and mockups for invitations. Evernote syncs across all devices, which is helpful when meeting with photographers or venue managers.
Premium Evernote ($70/year) is required to attach PDFs and add notes to it, receive 10 GB in storage, and plenty more.