Nothing sparks a heated debate among my fellow sommeliers as surely as the subject of corkage.

This is a vastly misunderstood topic. For diners who like to take a treasured bottle from their collection to share with friends in a restaurant, corkage charges vary widely, from a reasonable HK$150 per bottle to well over HK$600, depending on the establishment. It's fair to say that, in general, high-end restaurants charge more for corkage.

For a restaurateur, it is a minefield. Corkage is charged because a guest is using the restaurant's staff, who open the bottle and serve the wine, and its glassware and decanters. Many restaurateurs also see this as a missed opportunity to sell a guest wine.

Often, regular customers consider it their right to bring a bottle and not be charged corkage (oh, the huge arguments I have seen on this topic). That guest also expects his or her bottle to be served with the same reverence as if it had been ordered from the wine list.

So what is fair corkage? I think it should be the average price of a glass of wine multiplied by the number of people at the table - so, for four guests at an establishment charging, on average, HK$100 per glass of wine, the corkage would be HK$400. Magnums, as they obviously hold more wine, should have a corkage charge 1.5 times that.

I've dined at restaurants that have outrageously high corkage charges.

A visit to a Middle Eastern-themed restaurant a few months ago had me fuming: the corkage charge was HK$600 - much more than any of the bottles on the paltry wine list. The owner's explanation was that he didn't want people to drink their own wine in his restaurant. What made the situation worse was that three of the 10 wines on the list were unavailable.

Another bone of contention comes when a new restaurant is awaiting its liquor licence but still charges corkage. This is unfair - if they can't offer you wine, the management shouldn't charge you for bringing your own bottle.

If you're dining out, make sure the wine you take isn't on the restaurant's list. It should be a special bottle, not plonk from the sale section of a supermarket.

I am sure that all my fellow sommeliers will agree on this point: the offer of a generous sip from a bottle that has been carefully decanted and served is very much appreciated.

A guest who does this may be presented with the bill only to find the corkage fee has been waived.

Nellie Ming Lee is a food stylist and part-time sommelier studying with the Court of Master Sommeliers.