What is the most logical next event?

How to have a car boot sale
Make sure you're allowed to have a car boot sale.
For example, in the united kingdom, it's required that you get a license from your local council first. Knowing you have gained the proper permissions for a sale will give you peace of mind and help you avoid a fine, as well as reassure customers you are not a troublemaker.
Go through your possessions and work out what you want to sell. Go through all your rooms, draws and cupboards.