Don't worry about not qualifying for insurance when you are older. A prevalent myth perpetuated by the insurance companies is that people should buy insurance when they're younger, because it will be much harder to qualify for the policy at an older age. Insurance isn't any easier to get when you're young than it is when you're old. It may be cheaper, but that's it. The reason insurance providers want you to think insurance is easier to get when you're young is because the longer you have insurance, the more money they make. Most young people don't die from sudden freak accidents and, instead, live into old age.
When buying a policy, you want to cover your debts. If you have a car loan for $20,000 and a mortgage for $100,000, you need at least $120,000 in your policy to cover these debts and maybe even a little more to cover interest.
You also need to take your future obligations into account. Will your daughter be getting married in the next few years? Do your children need college tuition in the future? Think of all the large expenses like these that will come up over the course of the next few years, estimate their costs, and add that amount to the coverage amount you need.
Income replacement is another important factor to consider. If you make $40,000 a year, probably you'll want to get a $500,000 policy plus however much you need to cover debts and future expenses. You want to make sure your dependents can move on without being mired in debt or not having money for rent, food, gas, or other necessities.
Determining how much life insurance to buy is easy, when you sit down and think about it!