Obviously you need cakes but we will come to that another time , but here we go.
1. A nice big table
2. A nice big table cloth. Paper will do or even a plain coloured cotton sheet
3. Paper plates , bags, labels, tongs, rubbish bag, lots of small change, (Your first customer will buy one muffin for 30p and offer you £20 note, I think that they hope you will just give them the cake to go away), pot for money - the margarine container you emptied whilst making the cakes is good, the egg box less so. An apron to wear (optional) but make sure you have clean easily washable clothes on. Hair tidy and clean hands
4. Customers! Advertise your sale at least a week in advance. Posters, flyers notice in local newsletter, paper etc
5. Get as many people as you can to bake a cake(s) for you so that there is a wide selection. Try and get some idea of what the person will make. 300 choc chip muffins is not my idea of a selection and a selection is not burnt/undercooked some the dog chewed and some my brother poked with a pencil all different but not what I had in mind.
7. If you helped with a cake sale you will know what sells well so make a good choice and make a few of say 4 different kinds. Some cakes sell better at different times of year sponges in the summer and fruit cake in winter.
8. Pricing, always a thorny problem. From the practical point of view only price in round amounts eg. 20p, 40p, £1, £1.20 etc. Don't undersell yourself. Look at the item and think "would I pay 40p for that muffin? Yes. 60p? Yes. 70p? No", so 60p is probably right. For larger cakes I take a base line of a one pound sized loaf shaped plain cake such as a lemon drizzle or seek advice from someone you know who has done it before and has a practical grasp of the real world and you can always reduce the prices if thing don't sell.[ ;-) ]. Also if you have small cakes at say 30p put four on a plate and sell them for a £1, people like to feel they are getting a bargain and they were really only going to buy 3 and you have made them spend more already.
9. Ready? GO! You will be swamped with customers and everything will have gone in 30 mins, 40 max.
10. Beware of a) small children with sticky fingers who will paw everything and b) people who say "oooo that's dear I'll give you a £1 (for a £2.50 cake), you won't sell that at that price" be polite and say "Come back at the end and we'll see", they won't and you won't have any thing left anyway (they are probably the owners of the children with the sticky paws.
11. Go home and count the money, wash all clothes which will be sticky and stained with chocolate and have a nice cup of tea and a McVite's chocolate digestive or anything you have not made!