Sex, violence, foul language, drug use, adult themes. It seems as though these are the ingredients in a moviemaker’s spice rack. The amount of such “spice” determines the movie’s rating: G, PG, R, etc. (It’s like an Oriental menu, where each meal gets more stars the more it will burn your mouth.) Seems pretty straightforward.

But the Motion Picture Association of America (MPAA), which produces the ratings, is under attack from frustrated moms and dads. They say it isn’t helping them determine which movies are appropriate for their children, which is exactly what the ratings system was intended to do.

How do movies get rated? The MPAA board is an anonymous group of about a dozen parents living in the Los Angeles area. They each vote for “what most parents would consider to be that film’s appropriate rating,” according to MPAA President Jack Valenti.

There are only a few hard and fast rules—certain words or images that will automatically bump a film to a sterner rating. But mostly it is left to the board’s discretion.

Some parents gripe that often the ratings seem arbitrary. In terms of objectionable content, PG-13 films, for example, can be “the widest possible range from innocuous to really appalling,” as Nell Minow, author of The Movie Mom’s Guide to Family Movies, put it. Fire has even come over the tame G-rating: Parents say they have scenes much too intense for their small children.

So what can one do? Some are taking the matter into their own hands, publishing books and websites with detailed information about objectionable content in specific movies. One such site, “Screen It!”, goes so far as to list each film’s entire rough vocabulary, along with the number of occurrences. The same for a list of 14 other categories of potentially “overspiced” material.

The fact is, you need to make wise, educated choices about which movies you see. Don’t trust the judgment of a few L.A. parents: Learn to exercise your own judgment.

That means watching for clues as to whether or not a film is worth your time in reviews or previews you see or comments from others you may hear.

And it will probably mean passing on a movie that “everyone” is seeing, or maybe even walking out of a theater from time to time if you find yourself getting indigestion from something too spicy.