It seems around here we give the finger by holding our hand in a closed fist, thumb across fingers, middle finger extended.
But I see on TV sometimes that some fold their knuckles down, thumb extended out and middle finger up high. I first noticed it on The Walking Dead when Daryl and Beth (rest her soul) were flipping off the cabin they set on fire. Something looked odd about how they were giving the finger and then I realized the difference.
What’s your preferred way to flip someone off?