Regardless of the withdrawal schedule, the deadline is important. The IRS penalty for not taking an RMD, or for taking less than the required amount, is steep: 50% of the amount not taken on time. The deadline to take your first RMD is normally April 1 of the year after you turn 72, and December 31 each following year. Note, however, that if you choose to wait until April 1 of the year after you've turned 72 for your first RMD, it will mean taking 2 RMDs that year, and the additional income could have other tax consequences.
Many people choose to have taxes withheld from their RMDs, as it is counted as ordinary income. If you choose not to do this, make sure you set aside money to pay the taxes. And be careful—sometimes underwithholding can result in a tax penalty.
Below is Uniform Lifetime Table that you can use to figure out life expectancy factor: