If you turned 70½, last year you should have taken your first RMD by the end of the year, unless you elected to defer your first RMD until April 1 of this year (see First Year RMDs).
Your RMD for each year will be calculated the exact same way in which your first one was (First Year RMDs). The only difference will be that you will be using the account balance as of the end of last year, and your age will have increased by one, so the resulting Life Expectancy Factor from the appropriate table will have changed.
The only other change would be if you change your designated beneficiary resulting in the use of a different table than you used in previous years.
Withdrawing Your RMD
Once you have determined your RMD amount for the year, you must withdraw at least that much from your account by the end of the year. To elect your withdrawl simply complete an IRA Distribution Request Form, using “Normal Distribution” as the reason.
You may wish to satisfy your RMD on a more automated basis. The best way to accomplish this is to determine your current RMD amount, then determine a periodic (monthly, quarterly, etc…) installment payment that could be initiated that would satisfy your RMD for the year. To reduce the frequency in which you will need to alter this installment schedule, you may wish to take a little more than required.
Since your balance will fluctuate with any gain/losses on your account, it is still your responsibility to calculate your RMD annually and ensure that the sum of your installment payments will satisfy your RMD each year.
For all years after the year in which you turn age 70½, you must withdraw your RMD by December 31. This means that if you chose to defer your first RMD until after December 31, you will need to take a second RMD in the same tax year (your first RMD and the RMD for the second year).