Fill containers you’ve saved from the nursery with good-quality soil (be sure to rinse pots before using). Place your plants in the right size pot.
Place notices around the neighbourhood, in the local paper or send an email to your friends. Facebook is a great resource for listing events.
Group pots by growing requirements and type. Set up an umbrella for shade plants. Determine pricing ahead of time and create signage.
Label each plant with pertinent info (see Anatomy of a plant label for an idea of what you'll need) and be responsible about noting if a plant is a spreader or should be contained.
Have plenty of change for twenties and be ready for questions. Have
you experienced problems with pests? When does the plant bloom?
Make arrangements to give leftover plants to a local school or community garden. Also, you could consider donating the proceeds to a charity you support.