For those readers turning 70 1/2 this year, with Traditional IRAs (TIRAs), don't forget your first RMD is due this calendar year, unless you elect to defer to 2018 and withdraw both 2017 and 2018 in 2018. My back-of-the-envelope suggests a deferral could have adverse tax consequences.
So, assuming you plan to withdraw your 2017 RMD in 2017, be aware that some financial institutions require "paperwork" (e.g., Schwab), and that it's not necessarily like Vanguard, where you can just pick up the phone and order an RMD.
In addition, if you plan to satisfy your total TIRA RMD from one IRA account (as did I), make sure you won't get socked with an EWP. Some IRA CDs permit RMDs from IRA CDs with no EWP, but only "to the extent of" your RMD on that particular institution's IRA CD. Amounts in excess may be hit with a nasty EWP.
Bottom line: don't wait until the last minute to order that RMD. If you have questions, pick up the phone.