[€uroMeinke]

It's situational - sometimes you just can't accomodate another person. Weddings can have a huge per person cost sometimes, but even dinner reservations can create trouble if you "just add one more." I think those times it's easy to decline the request for invitation.

Other times, the person is just too annoying to accomodate for whatever reason. That's a bit more difficult if you have mutual friends and such. Often this is a huge source of Drama that begins somewhere when your a kid and someone has a birthday party. The Big thing to do, of course is invite everybody and let them self select about whether or not they go - I've found this is often the best solution.

Still there are those people you'd rather not deal with. I think the Miss Manners approach to put this off, is a simple, "I'm sorry but we can't accomodate you this time." Offer explanation or excuse - as that's a "problem" someone might try to solve. so just you may have to learn to say no in several different ways.