It is important to think about how you will transport and store your food products, so that they can be sold in a good condition. Think about ways you can reduce potential damage from impact, sunlight, condensation and squashing.
As with most trades you need to think about labelling and packaging. Make sure your labels are honest and factual as well as inviting. Your display good have a theme that will help attract people to your table. Think about the height of your display. People need to be able to see it, but not too high that it can be knocked over.
You will need a food hygiene license.
It can be a good idea to have a well recognised and popular type of product with a little twist that can make it interesting. Like gluten free or made with honey rather than sugar.
You may be able to supply to local cakes at your trade price as well as at your retail price at fairs. You could also look at local businesses to sell directly to. Having a heather option is always popular.