Beware of hovering — it has the potential to seriously freak people out. By lurking, you can make a person uncomfortable. Most people can sense when a person is silently hovering near them, and they can take it as a signal to move far, far away. Even if you don’t mean to be creepy, you never want to make someone feel unsafe.
On a related note, be sure to pay attention to what this person is doing. Do they seem like they want to be alone? For example, if your crush is the receptionist at an office, keep in mind that they are working and are most likely extremely busy. If they seem open to talking, you can consider striking up a conversation, but be sure to respect their personal space.