Shadowing

Hiding and Sneaking allow for you to move unseen and unheard, and can be used to follow someone, but is impractical in a public or otherwise populate location, privy to the scrutiny of many other people. In this case, Shadowing is the skill of choice, being able to tail a person without being noticed. Sometimes this involves sneaking, but more often than not it requires nonchalance and hiding in plain sight.