What should I do in the last 12 hours of the launch?

Be much more active on PH, and try to answer discussions by mentioning that you'll launch soon. Creating a discussion about your launch and AMA can also help in your product awareness prior to launch.

- Share your launch on all your social media channels - Reach out to your users / email list and remind them to upvote your product - Ask your friends to upvote your product - Always standby - Monitor your analytics - Keep the momentum going by continuing to promote and engage with your users

relax, everything should already be done. plus launching isn't a tidal wave, its a rock being thrown into the ocean

Drink a glass of still water, breathe normally, feel proud :-)

Create a launch checklist in advance, and set expectations for your key stakeholders as to how they can support you immediately after the launch. Then, all you have to do when the time comes is execute.

Staying active and engaging your community always helps!