Make sure to publish the rules of your hack day. Include: IP ownership, off limits systems or data or any other rules specific to your business. Create a schedule including, starting time, finish time, presentations and wind-up. Arrange coverage for OPS and on-call if necessary. Don't forget to add the schedule to everyone's calendar! Publish lists of teams and team projects and encourage people to sign up for the teams.
Provide technical info of network connectivity, available resources, aource control, access to datasets and anything else that may speed up development. A great way to increase productivity on hack day is to provide virtual machines on a service like AWS or in your data center. Be sure to test connectivity and install the software and developmen environments your teams will need. If there are restrictive policies on connectivity, software installs or data, now is the time to provide alternatives. If you use a service like AWS, Establish a resource suite for each team - ELB, CloudFront, S3, pre-configured EC2 instances and RDS.
Encourage a broad group of people to join hackday teams. A hack day isnt' just about new technology or business ideas it can be a good way for people in the office to get to know one another and to appreciate everyone's contribution.
On Hack day the aim is to make everything run as smoothly as possible. Keep the team's attention on projects by removing any ostacles to productivity. Provide as much technical support as possible - screens, connectors, printers, color printers - anything to make the end result simpler and easier to produce and demonstrate. Don't forget to provide IT support, supplies, and breakfast and Lunch (Dinner depending on schedule). Elect one person as facilitator. The facilitator won't join a team but will walk around between teams and solve any problems or issues that crop up. Take lots of pictures and video.
A few days after the Hack Day event get feedback from developers, product, qa and ops about the hack day: What worked, what didn't. Try to meet with and get feedback from leadership on the hack day. About a week later, hold a retrospective on what went well, what could be better or improved.
Create a presentation using documents from the Hack Day event. Include lots of photos and video. Try to summarize each team's contribution. A few months after your Hack Day, follow up to see if any of the hack day projects have significantly impacted project features and business goals.
Prepare for your next Hack Day!
The Hack Day Manifesto has some great information about hosting a public Hack Day
This article by Tim Blair has some good advice including an example proposal to management.
Knight Labs shares some lessons learned from 3 hack days. Making paper prototypes is a great idea to really get the creative process started.