Room them somewhere north of Siberia, without a phone or a TV. When they ask for a meal tray, tell them that you only serve meals at designated times. Period. The doc will more than likely recognize the patient's name and, presuming it's the usual symptoms or complaints, leave them waiting for a long time -- so long that some will decide to leave. If they come in drunk, they are required to either a) commit to detox or b) remain in ED Siberia until a breathazlyzer registers zero. If there's clearly nothing wrong with them, remind them early and often that they will have to arrange their own transportation home (presuming, as my hospital does, that yours no longer provides cab passes). And if the patient is unhappy with their care (i.e., prescription), make sure you chart any remarks along the lines of, "Well, I'll only come back tomorrow," each and every time he or she says it so that your department head can report them for abusing the system. That's what enabled our local paramedic service to refuse to stop transporting two FFs several times a week.
Sometime in the past year, I saw an article -- on Medscape, I think -- about how to deal with "ultra-high frequent fliers." Maybe it offered some helpful information, but I'll never know. I couldn't get past the definition of an ultra-high FF as being 15 or more ED visits a year. Seriously? Our champs rack up 100+.