Hello, and welcome to KnittingHelp.
I don’t have any experience of selling at craft fairs, but I have done my share of toy fairs and boot sales with my late father.
In general you should expect the following and if things are better count them as a bonus:
You will have a long walk from the parking area to the entrance and then to your stand (if you are on a different level to the entrance assume lifts are non-existent or out of order). Remember you’ll have to get your stock from your vehicle to your stand so a collapsible Sack Truck or similar is useful.
Your stand will be the one in the gloomiest part of the venue. Bringing additional lighting in the form of free standing spot lights is useful. Also bring one or two multi-gang extension leads in case there is only one power point near you and/or the nearest one is located by the next booth.
Allow more time to get there and set up then you think you’ll need.
If you can take someone with you, do so. As well as help setting up and someone to talk to in quite periods, they’ll also be able to look after the stall when you take a bathroom break. If you can’t get anyone to go with you make friends with the person on the stall next to yours and offer to return the favour of looking after their stall for them when they need a break.
Once the public are admitted it will probably go to one of two extremes, either it will be really busy and you’ll be rushed of your feet, or it will be mind numbingly slow.
The public in general will either be wonderful or so jaw dropping stupid you’ll wonder how they made it out of the womb without the aid of a sat-nav!
The business card are a good idea, but I would put to washing instructions with the hats as the hats and cards could get separated in the future.
With regard to cost, are you intending to do this as a ‘one off’ event or to do more of the same in the future? If you intend to do more you need to ask yourself what will be the cost of purchasing the yarn to make a complete hat? It’s better to price as if you had to buy the yarn from the start. Is the 9-10 hours for 1 hat literally that amount of time or does it include ‘down time’? As you do more hats you’ll get quicker at them.
If the person who suggested you sell the hats at $15 each has experience in this market go with their advice. One of my father’s observations was ‘If something’s too cheap, people won’t buy it’. In fact I would be tempted to mark them up at $20 each and if someone is undecided between two hats or things are slow you can always let them go at 2 for $30.
I’ve probably made it sound a lot worse than it is, but I’m one of those people who prepares for the worst and hopes for the best, so everything will be a lot better for you on the day.