Stricktly before December 31, since that is a Saturday and your broker may not honor the request until January 2 2012, and that would be too late. Better get your request for the rmd Friday or maybe Thursday depending on how efficient your broker handles withdrawals.

This is too late to guarantee that an RMD will be processed. If you are cutting it this close, go to a local office to take the distribution and not try to setup a reoccuring RMD for that year.

I recently helped my SIL setup her RMD, I believe the forms stated a month was required.

Also, December isn't a great month to take an RMD. We setup her RMD to be taken evenly across 3 distributions during the year. The forms allowed monthly, annual or a selection of specific months during the year.