"Repairing disk permissions"... when should this be done, and how?

Repairing Disk permissions is recommended right after installing (anything...).
You can do it via *Disk Utility*, which should be in your Applications/Utilities folder. Open it, select the disk you want to repair, and click the (guess which!) button:
!http://farm4.static.flickr.com/3103/3989417945_18c460d616.jpg!

regards, Erik.

repair disk permissions is for old ladies. It's like a mac-myth: "if it aint broke, repair disk permissions"....

slidersson, that is simply incorrect IMHO. Screwed up permissions can cause a myriad of problems. I advise my clients to repair permissions every couple of weeks and they all report improvement in OS stability.

There's a lot of debate over whether repair permissions is really a good maintenance tool for regular use, you may want to read into what it actually does before making this a part of your routine. Yes, it will help if your system has problems +caused by incorrect permissions+, but it isn't a catch-all fix. The reason it is recommended by so many people (IMO), is that for the majority of users (i.e. people who don't mess with disk permissions on their own), it is very unlikely to do any harm, and it could be helpful. Basically, for those of us who don't really have the skills to track down the cause of specific problems, it's a quick process that may or may not correct the issue.

There was a really helpful sticky thread on this subject a while back (I believe in the Leopard forum), I'll try to see if I can dig it up for you.

Exactly. It can't hurt and sometimes, frequently in my experience, it helps.