I put in a good many years as a devoted writer of letters to the editor before I found myself one day on the editor's side of the mailbox. So I can readily understand readers' curiosity about the process of choosing and editing letters for publication. 
Preparing copy for the Readers' Forum is part of my job as editorial page editor.
Sometimes, though, especially when they are displeased, people don't ask me what happened: They tell me, often providing elaborate explanations based on the motives of some unspecified "they" who apparently have taken over the letters page when I wasn't looking.
It's hard for me to understand how the callers can be so certain when they're wrong.
"Why aren't you publishing any letters that say . . ."  those calls usually begin, and the simple answer usually is "because I don't have any right now."
I don't think anyone has ever called to complain that I wasn't publishing enough letters the caller disagreed with.
If we have enough letters on a particular topic that I have the luxury of choosing among them, I count them and publish pro and con letters roughly in the proportion we receive them. I don't really care which side of an issue the writer picks. If it  bothered me to read things I disagree with, I wouldn't be doing this job.
But if the writer's point of view is rarely a factor in whether a letter is printed, some things related to content do matter, and the most important of them is libel. We don't want to be sued, not even if the suit is without merit.
Let me share part of a letter we didn't use in Readers' Forum. The author, who is Latina, went to the movies with two friends. With neither the theater nor the city identified, perhaps it will cause a whole lot of theater managers to give their staff members a heads-up.
"I was translating some of the parts, whispering so as not to bother anyone," she writes. "Then the manager came to me and in a very rude manner told me to 'shut up.' I told him he should talk to others who were louder. He left very upset only to come back later with a worse attitude and this time he threatened to call the cops. A few minutes later, not one or  two but three police officers arrived. How embarrassing!
"This manager singled us out. Was it because of our dark skin? Because we were three women? Why didn't the manager send the cops to the other people talking?"
I have no reason whatsoever to think the writer is being untruthful. But on the other hand, neither do I have any independent verification, and there could be more to the story than the writer knows. So we didn't run it.
If the incident were more serious, we might assign a reporter to do a story rather than just publishing the letter. The tip leading to Wednesday's page-one story in the San Ramon Valley Times about a young man's complaint that police used excessive force in arresting him was a letter from an indignant observer.
Some categories of letters are seldom or never considered for publication. We don't do poetry. Frankly, the people who write it usually don't do poetry either.  Also, publishing one just encourages hordes of others.
We don't print sermons or prayers, although religious arguments on issues are as appropriate as any other kind of arguments.
And we generally just toss mass mailings or faxes from distant cities.
But most of the boundaries are elastic. We prefer local letters, but that stretches to former residents who want to comment on local events. It's nice to know that people clip and copy articles for friends and relatives now far away.
We edit out obscenities and slurs, but the Readers' Forum would be a pretty dull place if we excluded everything that offended anybody. It would be slightly less dull if I just excluded everything that offended me, and didn't worry about anybody else, but I don't think that's what the letters column is for. Many of the most urgent issues of the day can hardly be discussed without offending somebody.
Illinois Sen. Carol Moseley-Braun once proclaimed "I have a constitutional right not to be offended!" but of course she doesn't.
I'm a columnist, and if I never offend anybody I'm not doing my job, so I'm fair game for angry letter writers as long as they're not factually inaccurate. After all, I know I'm not going to sue me. But we don't allow reporters to be criticized by name — they may not be responsible for whatever irritation prompted the letter. And we edit out or tone down personal attacks on people who are not public figures. Better not to make them.
Because our space is limited, we limit the length of letters as well. I can stretch the 200-word limit a little, maybe 10 percent, but anything longer requires special dispensation from my editor, and it's not usually forthcoming. All letters are accepted subject to editing, and if you insist on sending me 500 words, I'll cut it to fit. We'll probably both be happier if you do it instead of me.
 Occasionally, especially around election time,  we have a wealth of letters and have to choose a representative sample. But most of the time, if a letter is publishable at all we'll print it. Those are good odds. Give it a try.