1) The person you want to insure for life insurance agrees to allow you to take out a life insurance policy on their life.
2) There is an "Insurable Interest" between you and the person you want to insure for the life insurance coverage - (e.g. buying life insurance on a family member, or setting up a key-man or buy-sell agreement between business partners of a company).
3) The life insurance policy being applied for is suitable to the need. There are limits to how much life insurance coverage can be taken out a person - Usually 20 to 30 times income of the insured person - exact maximum coverage allowed varies by the life insurance carrier.
When applying for a life insurance policy on another person you may need the person's permission, signature on the application, and the person may need to answer some health questions.
Learn more about how to buy life insurance for another person.