The fair can be a lot of fun, but it can be a budget-buster. I've learned a few tricks over the years to keep the costs down to a dull roar:
Look for discounts: In most cities, the fair teams up with drug stores, groceries or AAA to offer advance-sale admission or ride tickets. Most of the time, "advance-sale" is a loose term; tickets are available through the entire run. Some fairs also have special admission days: show your grocery store or drug store loyalty card and get $$ off. Also, in my city, the local newspaper has been known to run 2-for-1 coupons for select days.
Parking: In my state, you can get free parking on the grounds until the lots are full. If yours does too, be sure to get there early.
Food and drink: As far as I know, nobody offers discounts on deep-fried Twinkies. (and I've found that food prices don't vary much from booth to booth.) But, if your fair allows it, you can always bring in some portable snacks -- fruit, energy bars, crackers and the like.
DH and I make sure to have one square meal during our stay. We've found the pork, beef, lamb and poultry producer's tents offer good-sized meals at a reasonable price. And hey, it isn't the fair without a nice ear of roasted corn ... dripping in butter, of course.
As for drinks, our fair is cool about bringing in a bottle of water, which can be refilled at the water fountains. When I was a kid, my mom used to bring those collapsible cups to use for splitting drinks or filling at the fountains.
Rides: We're not midway fans. But if you are, again, look for the discounts. Check the fair schedule for 2-for-1 days, or all you can ride for 1 price days.
And if you're a fan of free samples (and other assorted plastic dodads), then grab one of those plastic bags and fill'er up. Last year, we wandered by a booth offering antacid samples (appropriate, don't you think?). Business must have been slow -- these guys gave us handfuls of samples. I still have enough to get me through the most fire-filled chili suppers!