USAToday provides some annuity tips:

In its simplest form, an immediate annuity is a contract with your insurance company. You pay the insurance company a lump sum — say, $100,000 — and the insurance company agrees to pay you a monthly amount for life.

According to ImmediateAnnuities.com, the average 65-year-old male would get $598 a month for life from a $100,000 deposit.   Planners typically advise that you take about 4% a year from your savings if you want your money to live longer than you do. At that rate, you'd pull $333 a month from a $100,000 account. So an immediate annuity would give you a larger payout than a conservative withdrawal strategy.

Naturally, there's a catch. In the simplest form of annuity, your heirs get nothing if you get hit by the 5:19 Cannonball a year after signing the contract. The insurance company gets the unpaid balance.

Pocketing those unpaid balances is one way insurers can offer a higher payout than the 4% rule. Your insurer doesn't know when you will die. But in a given pool of 100,000 annuitants, the insurer knows that half will die before they reach median life expectancy, and half after. Money from those who die early go to those who live longer than expected.

RetirementThink Income Annuity Basics