NEW YORK (CNN/Money) - You're out to dinner with a group of friends. The total for your meal comes to just half the bill rung up by Diamond Jim and the trust-fund twins across the table.

But, of course, good 'ol Jim -- being an equal-opportunity bill payer -- suggests you all just split the check evenly. (After all, who wants to ruin a good meal with arithmetic?) Not wanting to appear cheap, you shell out the extra dough and quietly seethe with resentment.

Faced with Jim's poor money manners, that was probably the best you could do. Let's not be too hard on Jim, though. Few of us are perfect. You may have unknowingly made a few money faux pas yourself.

Perhaps you make much more than your old college roommate, who's now a third-grade teacher. You've always heard teachers are underpaid; you just never knew by how much. So you can't figure out why your friend won't tell you what she makes. "C'mon, what's the big deal?" you say. "It's only money."

You then follow up this thoughtful remark with a comment about how house values on your block have doubled since you bought your home for $250,000. Your friend offers a vacant smile and makes a mental note never to see you again.

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There's no end to the ways money can ruin a perfectly good evening -- or relationship. Money is always a big deal, which is precisely why it's important to handle the subject deftly with friends and colleagues.

When you're out to dinner with friends, "plan to pay more than what you spend," said Jeanne Comeau, director of the Protocol School of Boston. "Accounting at the end of a meal can make an otherwise lovely evening less lovely."

Peggy Post, spokesperson for the Emily Post Institute, puts it another way: "Nickel-and-diming puts people on edge."

Of course, you're usually talking about a lot more than a few dimes when it comes to subsidizing someone like Diamond Jim. The gracious thing to do for people who order the most expensive meal is to offer to put in extra money. But if they don't, you're stuck. It's just bad form to insist that you ordered less and therefore should pay less.

Some people, burned by too many unexpectedly pricey group dinners, decide to do as the Romans do and start ordering the filet mignon, since they're going to pay for it anyway. That's understandable, but not necessarily the most considerate move, Comeau said.

The thoughtful thing for everyone to do at group dinners is to order mid-menu items, she said. That way, when the bill is split evenly it really will be more of an equitable division and you don't tack on more to the bill than others at the table might wish to pay if they order lower-priced items.

Of all the breaches of money etiquette, nothing is more intrusive than someone trying to fish around for what someone else makes. Whether a person is brash enough to ask straight out or tries to deduce your salary through prying questions, such as whether you qualify for a Roth IRA (your adjusted gross income must be below a certain level), the effect is the same: You feel put on the spot.

Most people are hush-hush about what they make because they know they may be judged differently when others can pin a number on them. So even if you're above such calculations and are happy to volunteer your salary information to a friend or colleague, don't expect reciprocity, said Hilka Klinkenberg, managing director of Etiquette International.

Generally speaking, the only people with whom it's appropriate to discuss your salary are: your boss (the one who gives raises, not the 10 middle managers in between); your spouse or intimate partner; and your banker or financial adviser, she said.

If asked about your salary by people who have no right to such information, you can always reply, "That's confidential, " or "I consider money matters personal," experts recommend. Or you can lob a question back at them: "Why do you ask?" If the person wants an idea of what a position like yours pays, you might offer a broad range such as "between $50,000 and $100,000, depending on tenure and experience," Klinkenberg suggested. Or, better yet, just direct them to human resources.

Living in a consumer culture, it's tempting to talk about things you bought and to ask others about their purchases. That's not always taboo, especially if you're talking about small items or great bargains, or if you're talking with a close relative or friend.

But, generally speaking, "How people spend their money is a private issue," Klinkenberg said.

Take the engagement ring. When a woman gets engaged, feel free to tell her the ring is lovely but don't ask her how much her fiance spent or how many carats are in the ring. "The money spent on an engagement ring is no one's business," Post said.

To deflect further discussion, a bride-to-be might simply say, "I don't really talk about those things." Or she might throw the question back by saying, "Why do you ask? Are you getting engaged?" And then steer the conversation towards a more general discussion on ring-buying.

The same advice goes when you're faced with questions about how much you paid for renovations, a car or your suit. And even in cases where the money spent is a matter of public information, such as what you paid for your home or the cost of your child's tuition, "Most people don't liked to be asked these questions," Post said.

What's more, volunteering the information yourself may be perceived as bragging, as in "Look how much I can afford," experts said.

As a general rule, "The only money that's your business is your money," Comeau said.

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That holds doubly true when you consider talking to someone about another person's financial circumstance, such as your spouse's inheritance or a colleague's credit card debt. "It's being indiscreet and disloyal," Klinkenberg said.

Not to mention risky. You can't control whether the people you talk to will keep their mouths shut, so you never know if or where the information will travel. The same can be said when you reveal your own personal financial information. "You have to be very careful about who you grouse to," she warned.

If you really want to steer a clear path through money minefields, the bottom line is this, Klinkenberg said: "You can never go wrong by not talking about money. But you can very easily go wrong by talking about it."