I have been doing craft shows for over 6 years now and I certainly can help you with your questions.
1. In my dealing with organizations that want a percentage of sales, it is based on your booth sales. Just like Julie stated.
2. I, myself, have never run into a craft show asking for insurance. I am sure you can always ask the person running the event.
3. I use a sales book, carbon free, so you can keep track of your sales, the items sold, and the customer gets a receipt. I usually put my name, email, and phone number on the receipt, if not a business card, so the customer knows where they got the items from.
Its also good to keep an inventory sheet so you know what has sold, what is popular, and what just sits around.
4. Absolutely, use an old school photo, maybe have an old yearbook, and its always nice to read a bio on the crafter. They are great icebreakers.
Also if you have an Ipad, take your photos and run a slideshow of the items you have made. That gives the customer an idea of the things that can be made if you don't have any at that time.
Have fun, and don't be discouraged if you don't make a lot of money. It takes time to get a customer fan base. You might also want to have a sign up sheet with email, to let your customers know where you will be at the next show.