As someone who has driven commercially for years, it dismays me to witness the confusion and panic of my fellow drivers when approaching this fairly common and rather simple intersection.
For the sake of their peace of mind, and because better drivers make Everyone safer, I thought I'd take a moment to explain the few basic rules to keep in mind when confronting this crossing conundrum.
Simple Rule Number 1:
First Come, First Serve.
This basic guideline should cover 99% of your needs at a 4-way stop.
If you haven't stopped On the Line yet, you need to. The person who has been stopped the longest, gets to go next.
Plain and simple.
Generally, that rule alone should be sufficient. The odds of meeting at a stop sign at Precisely the Same Moment are pretty hard to gauge, but we can say they are pretty rare.
Often times, I will delay my stop by a moment or two of creeping just to prevent this from happening. By waiting to stop until After the other person has stopped, you can forgo the difficulties of the rest of these rules and stick to the plain and simple rule One!!
If you do find yourself actually stopped at the same moment as someone else however, luckily only a few other rules apply.
Simple Rule Number 2:
If you're Stuck deciding when cars are Beside each other, RIGHT Beats LEFT.
This means that if two cars are sitting at corners to each other, the one on the Right side gets to go before the Left side car does. Essentially, this means that cars go in a Clockwise Order.
This also applies when Three cars meet at the same time.
If two cars meet at exactly the same time Accross from each other, we get a different situation...
Simple Rule Number 3:
Between Cars Facing each other, STRAIGHT Beats TURNING and RIGHT Beats LEFT.
So, any car going straight through the intersection goes first, then any car turning right, then any car turning left.
Although, often times, - provided both cars are using their BLINKERS, it can be clear that both cars can go as they wish without impacting the other's movement.
Finally, if you happen to actually meet at an intersectional 4-way stop with 3 other cars at Precisely the Same Moment where all 4 of you are unsure as to who has the right of way to proceed, it is traditional to decide by the following:
Simple Rule Number 4:
If All 4 cars meet at precisely the same moment:
Each driver is to quickly put their cars into park, exit their vehicle, running Counter Clockwise, until they make a full circuit around their car while shouting "I want a Pony!"
The First driver to successfully complete their run and enter their car, then has the right of way to proceed through the intersection first.
Don't forget, just because YOU Know, Doesn't mean Anyone ELSE Does!
Drive safe!
@bokettoshiyou