There's a right way to say
There's a right way to say "no."

When you receive an invitation -- either verbally or via your inbox, mailbox or voicemail -- respond promptly. Whether your answer is yay or nay, it's inconsiderate to let the invitation simmer. Etiquette experts at Emily Post recommend replying within a day or two, and if you need to decline, do so politely to stay on good terms with your host.

Keep It Short

When you say "no," there's no need to explain why, states Elizabeth Howell of the Emily Post Institute. In fact, Howell claims it is rude for a host to push for an explanation. Just keep your response short and factual. Make it clear you appreciate being invited and say you won't be coming. Etiquette guru Peggy Post claims it's fine to mention a specific conflict if you want to, such as "I'm sorry I can't come to your parents' anniversary brunch. I have a dentist appointment." Or, writes Post, you may use more general language such as "I'm sorry we won't be able to join you for dinner. Nights are tough for us." Avoid going into detail if the truth might be insulting. Don't admit you'd rather go to your Pilates class than attend your friend's toddler's birthday bash. Instead, take Howell's minimalist approach and say "Thanks for thinking of me, but I won't be able to join you." If the invitation is for a one-on-one get-together, writes Howell, be extra warm and offer to take a rain check.

Good Form, Bad Form

In their book "Global Business Etiquette: A Guide to International Communication and Customs," authors Jeanette S. Martin and Lillian H. Chaney states if you're invited to a business associate's home for a meal, it's acceptable to decline. What's not fine, according to Martin and Chaney, is saying you'll come and not showing up. Emily Post concurs and adds that changing your "yes" to "no" is only acceptable in certain cases, such as illness or a death in the family. If you must cancel your plan to come, immediately let your host know. As far as changing your "no" to a "yes," do so only if the change won't inconvenience your hostess.