We started our safety process/policy when they could walk - setting the ground rules of staying with us and not wandering off and DEFINITELY not running away. We practiced every time we were in a store or public place and there was always a consequence if they tried to run from me. I did this with my oldest because I didn't want to look like a fool running after a toddler yelling his name and begging him to come back to me while he ran down an aisle giggling thinking it was a game. When the other two were born, they were only 19 months apart, so it was even more important - a 5 year old, 19 month old, and a newborn, plus I always had my toddler/preschool daycare kids with me as well. No room for running/wandering away nonsense in our excursions!
Fast forward 5-7 years and I didn't even think about losing my kids at Disney. No need for leashes, dog tags, bracelets, hand-holding, etc because we did all the practicing they needed from the time they took their first steps. Made it much easier on Mommy, and kept them safe!
Our family rule for *if* we get separated is, now that they are 13, 9, and 8 and are allowed to be anywhere in the same general area as DH or I - basically, if they can see us, they can go that far (it is their responsibility to make sure they can see us at all times), they are to go back to the place where they last saw me, because that is the first place I will go to look for them, and the place I will keep going back to to check to see if they got there. The child is to stay in one place (the last place they remember seeing me or DH or big brother) and the adults/teen will do the searching.
Boy! Thinking back to those toddler days....I am glad I was a "mean" mom!!!!