Your message should include your phone number

When you leave a message on someone's answering machine, voicemail, etc., always leave your phone number. Even if you think they know it, if you're wrong then they are going to have to go look it up, which annoys them and reduces the chances that they will call you back. Even if you know they have caller ID, they may be checking their messages from elsewhere, in which case the caller ID information on the phone you called is inaccessible. So, leave your number! Be sure to speak it slowly and clearly as well; I usually say mine twice, once at the natural point in the message and again at the very end. That way, they may have a chance to get a pen and paper before the repeat. The only exception to these rules is if you are positive that this person knows your number cold.

Talk to your potential future neighbors

When you're considering buying a house, knock on some of the neighbors' doors and ask them if there is anything you ought to know about the house. This can uncover problems such as noisy or otherwise unpleasant neighbors, future construction plans nearby, and all manner of irritations that do not have a material impact on the property (and thus that the seller is not obligated to disclose).

Always carry your keys

A piece of sanity-saving advice: Always carry keys, and spare keys. Never leave your house, even to get the mail, without a house key. Carry a spare car key so that you can get into the car when you lock your keys in it. I very rarely need to actually use these, but it's a tremendous stress reliever not to have to triple-check the doorknob to make sure I'm not about to lock myself out of the house, nor to ask my wife four times when we get out of the car whether she has the keys before I shut my door.

A similar tip: Always lock your house, car, etc. with the key. That is, shut the unlocked door and then lock it with the key, rather than locking it from the inside so that it's locked as soon as you shut it. (Using the car's clicker counts, assuming it's on the keychain with your car key.) If you need the keys to lock it, and it isn't locked otherwise, then there is no way to lock your keys inside.

Keeping baggies clean

My better half just showed me a great trick for keeping the outside of a zipper bag clean when you put something icky in it (in this case, bacon): Fold over the top of the bag the way you would a pants cuff, fill the bag, and then uncuff it and zip it up.

Online Organizing

Discovery of the day: OnlineOrganizing.com. Lots of info here, including an enormous trove of lists of organizing tips.