Don't agree that you will keep their thoughts of suicide secret. Let them know that you will be there to love and support them, and that you will need to get more support from professional sources. Don't try to handle a suicide person by yourself. Find out how the person plans to kill himself or herself. The more specific the plan, the greater the risk.
Some methods of suicide tend to be more dangerous and risky than others.
For example, if a suicidal person has access to a firearm, that represents a very high level of risk. However, almost all methods carry serious risk. If the suicide plan involves drugs, you may wish to call the poison control center in your area to find out what the risk is for the particular drug or poison that person is considering. Remove the method, such as the gun, pills, or knife. Call law enforcement if there is immediate danger involved to the person in crisis.