Eau Claire, WI rules as a kid:
Just needed a bat, a few balls, an open field (medium or large backyard would suffice) and anything that would work for bases such as paper plates, hats, tee-shirt.
Sometimes used a typical whiffle ball (you can make it do some weird curves and stuff as is) or duct tape/electrical tape the thing to make a solid ball, sometimes both can be used in the game. Sometimes, tennis balls can be used. Rules of engagement are set prior to the start.
In my day it was usually 4 vs 4, 3 vs 3, or if an odd number of players we used a dedicated pitcher. For example if we only had 5 kids it would be 2 vs 2 with the 5 kid rotating between teams as a dedicated pitcher and, theoretically, had no allegiance to either team.
- Pitcher's hand rules: since neither team could cover all the bases, if the batted ball was returned to the pitcher before the hitter got to 1st base = out. Tie goes to the runner.
- While the ball is in play and you beaned the base runner who was in between bases with the ball = out but the ball was still in play for other runners to advance. (especially fun if you duct taped the ball... it can leave a mark. Head shots count but it's easier to aim for center mass)
- Only one extra base on an "over throw" (while the ball is in play and was over thrown leading to it being out of the field of play, each runner can advance only one base).
- No strikes counted unless its a swing and a miss.
- 3 Foul balls = out. A "tick" is a foul ball. A "tick" is defined as a swing of the bat and it "ticked" the ball.
- Batted ball (in foul territory) over into adjoining cranky old neighbors backyard = out and batter had to hop over the fence to get the ball.
- Foul ball into the woods = out and batter had to fetch the ball, hopefully not come home with wood ticks.
- Batted ball over the fence deep center field in a neighbor's yard but in the field of play = home run.
- Batted ball landing on a roof is still in play and a live ball unless it gets stuck in the gutters while rolling down. Then a ground rule double.