A lot of customers attending craft fairs don't carry much cash on them (at least in my neck of the woods). They often will pay with either check or credit card. I would just make sure the phone number is on the check. If not, ask the customer what it is and write in on there. If the check is from out of state, you may also want to ask for a drivers lisence and write that number on the check as well as the state abbreviation. If you find you are going to do a lot of craft fairs, you might consider checking with your local bank to set up a merchant account where you can accept credit cards.
As for packaging, I purchased plain newsprint from Staples which I use to wrap my portraits. For smaller items, I use tissue paper. For bags, I purchased the brown kraft paper bags with handles for portraits and made a 5 x 7" logo sticker with my name, addy, web site, etc... on it. For smaller items I use either plain white plastic bags with handles or the ones that say Thank You on them. (Also purchased at Staples.) The brown handled kraft bags I got at a local party/paper dealer.
I try to remember to put a business card in each bag if a customer hasn't already taken one from the table. If you have other craft fairs lined up, you should print up some small flyers with dates and locations of your upcoming fairs. Put a copy in each customers bag. Some craft fairs won't allow you to put them out in plain site on your table. Be sure to read all their rules and follow them or else you run the risk of not being invited back next time or in worse case senario's being asked to leave.
Do Not sit and read the newspaper or a book. This tell the customer you're not very interested in their business. It's okay to have a seat during slow periods but if a customer enters your booth, be sure to greet them and stand up when you talk to them. Get to know your crafting neighbors. Often times they will give you some good tips, let you know of other shows, etc...
Good luck on your first show. Let us know how things went.
Linster