For us I judge the human attached to the leash and my gut about the dog. A few weeks back at the campground we were at has a large grass area, and the only area for dogs to do their business. There were probably 20 different dogs, our trainer with our 4yo had taught us the "proper" way to meet and greet dogs, and we let them meet several. All the dogs on site were all non-aggressive and amazingly most all of the owners were very well trained ;) So we did a lot of meet & greets - partially since we had our 4mo old pup and it was a good opportunity to learn from his older brother. Generally if we are just out we don't to random meets unless the handler specially asks if we are ok, IMHO those are the ones that understand the protocol and safety aspects.
