In a large saucepan or deep fryer, heat oil to 375 degrees.
In a large bowl, whisk together flour, milk, beer, eggs, and seasoned salt. The batter will be light and thin.
Working with 6 or 8 cheese curds at a time, add to batter, toss to coat, and remove with a wire strainer. Shake them to remove excess batter.
Drop the curds into the hot oil one at a time and fry until golden brown, about 2 to 3 minutes. Drain on paper towels and serve immediately with ranch dressing if desired.
Vegetable oil: Opt for a neutral oil with a high smoke point, like canola, peanut, or grapeseed.
Cheese curds: You'll find dozens of cheese shops, cheese stores, and even cheese castles on I-94 if you drive through the heart of Wisconsin. All the local grocery stores and Kwik Trips carry them, too. If you're outside the natural boundary of America's Dairyland, Target carries curds nationwide that are pretty darn good (my biggest complaint is that the bag is too small).
Yield: 1 pound of curds makes about 4 servings (4 ounces per serving).
Make ahead: Like most deep-fried foods, cheese curds are best enjoyed immediately.