For every mother in law joke out there there are two mother in laws who deserve that joke. That's not a scientific statistic or anything, but I'm sure we can all agree that seems about right. There are varying degrees of in law trouble, ranging from the vaguely annoying to the outright insane. For those of us who have in laws of the barely human variety all we can do is pray to keep our heads on. However, there are some tips that work great for the slightly annoying in laws that can even lend a hand to us whose in laws would require professional help.
The number one rule in my experience is communicate with your spouse. Not only can that help determine if your in laws are genuinely insane or if they just save all their crazy up for you and special occasions, but it is important that you and your significant other have a united front. That way parents can't go and complain to their kid about the horrible things their spouse has done. That keeps you and your spouse from being "in the middle" all the time, and also shows your respective parents that you agree on everything (even if you had to work it out first) and that they aren't going to get anywhere by appealing to their kid to change something they don't like. And there's always a lot they don't like, isn't there?
Secondly, pick your battles. If your father in law makes a snide comment about your jeans being "snug" chances are it's better to let it go rather than tell him all about how his clothes look. Not that you can't think it, just it's probably better not to say. However, when they jump in and try to make parenting decisions for you that's definately a good time to play ball. Try not to fight or blame or name-call (out loud) but rather state your decision in a firm way that sets clear boundaries. For example "I understand that you think it's okay for little Timmy to ride a motercycle, but we have decided that is not age appropriate and we do not allow our children to do it."
Which brings me to another suggestion-use the word we. Alot. That lets them know, even if it's subconciously, that you and your spouse are on one team together and that they can either get with the team or head for the door. A very important boundary thing.
If you have a significant disagreement, and you're in laws are of the generic not crazy variety, set a lunch date with them (bring your spouse!) to discuss your differences calmly and rationally. This only works for the non-crazy in laws, but is generally a good idea if it's possible.
If you can't say something nice don't say anything at all. It worked for thumper, and it can work for you! Or, if you must say something, say something polite but insignificant. For example-if they are going on and on and on about how your sister in law's child is so much smarter than your child you can choose to say something like "I'm glad that Billy is doing so well". Just try to keep the acid in your voice down to a minimum....then go home and scream in a pillow.
And finally, if nothing else works, put them in time out. No seriously. If they do something you find particularly atrocious, simply don't answer the phone for a week or two. Not only does it give everyone (meaning you) time to settle down, but it also becomes pretty obvious to them that you're not taking their calls and they will probably at least try to think about why that might be. Even if that doesn't fix their wagons, at the very least it will give you some time so that the next encounter you have with them doesn't end in bloodshed.
In laws are a tricky bunch. Some you can work with. Some you can't. Just remember-stick close to your spouse and stick to your guns and when in doubt put them in time out.