List the things that are a MUST have for you that they should know about, i.e., specific branding requirements, things that can’t be changed/altered, something they have to incorporate like a copyright notice, logo usage, etc. Don’t put too many restrictions in as you want them to be creatively free, but do include things you know will be an issue for someone later or that you want to make sure they think about and consider. Everyone has these, call them out early! Be sure to include the standard things like: include the corporate logo, tagline, website link, etc.