Doing a con requires three main components: Time, Space, and People. The time and space you can probably find or use with your organization, although there's something to be said about running a con during open hours, which means having to balance the needs of the people who are using the library and the people who are here for the con experience.
Planning what spaces you're going to use means knowing what space you have available! The easiest way to figure that out is to have a map of your building. Even if it's an emergency exits map, because you'll need to know about those, too.
Because you're likely going to be doing this event during open hours, think about how you can creatively use the space that you're in while not stopping the regular use of the library. Which might involve going outside, or having to drag and tape down an extension cord from one space to another so that events can happen in different spaces. Your building will fight you, because, for the most part, libraries were designed a very long time ago and their power and data fits and retrofits are meant for the last remodel's New Hotness, not what's going on right now. You'll have to be creative to work with your building's limitations.
You'll want a schedule of events and a program for your event. In addition to the schedule, you'll also want to print your space and behavior policies (if you haven't thought about those, you'll want to make them. Stop what you are doing now and create them.) so that everyone knows what's expected and how to report if someone is behaving outside of the guidelines. If it's not on the program, it should be prominently displayed for the event. Big signs that say things like "Cosplay is not Consent" with explanations are a necessary part of making your event safe for the most vulnerable attendees, and treating allegations of bad behavior seriously are necessary to making sure that people come back to your event.
Promoting the event sometimes means getting everything in to your Communications or Publicity Department and letting them do their magic for you, which can be great if your department knows what they're doing. If you don't have one, or they don't understand how to promote the event, you may have to do a certain amount of promotion and otherwise yourself.
- Local newspapers will usually print your press releases in various places if you give them with enough time to get them printed
- All of your social media platforms, official and unofficial, can become promotional vehicles to the followers you have
- Making short videos, either by yourself or with the help of volunteers, can make things even better for attracting attention
- Having fliers is also good for in-location promotion. The best thing to do for your events is to have a consistent visual presentation, logo, or mascot that shows up on all of the events that are related to this programming or theme. If you don't have someone with a graphic bone in their body, there might be a volunteer who would love to have the opportunity to design a logo or mascot character for you. Just make sure you get all the right releases and permissions, or that you have some money to commission them to get the character