If you are presently assembling the means of your own death, the time to go to the hospital so as to prevent yourself from killing yourself is now. As mentioned several times already in this article, you require immediate psychiatric care if you are feeling acutely suicidal. You need a safe environment to be in for a while where you can be protected from acting upon suicidal urges. You may also benefit from medication to calm you, help you sleep or to serve as an anti-depressant. Most acute suicidal urges pass, or at least decrease in urgency, after a period of time has gone by. If you can hold out and not act, there is a very good likelihood that you will shortly feel better. It is much easier to hold out and not attempt suicide if you are hospitalized in an environment designed to keep you safe, than if you are out and about in your normal environment.
Unless you have pre-existing arrangements set up already with a therapist or doctor, the only surefire way to get the care and safe environment you need is to go to a local Emergency Room (ER). Please go to the hospital immediately if you are acutely suicidal. Recruit a friend to take you to the hospital if you cannot get yourself there safely. As a last resort, you should call the emergency operator who can dispatch an ambulance or police officers to your location. This can be a rather expensive way to go, but if it is the only reasonable way to get yourself to the hospital, then don't let the expense get in your way.
It may cross your mind to call an emergency telephone crisis line such as those mentioned below. This is a good idea if you are just feeling vaguely suicidal and want human contact with someone who can help you work through your thoughts. If you are acutely and dangerously suicidal, however, calling a crisis line is not the best thing to do, as it will distract you from getting the hands-on assistance you need. In such a case, you really need the safe environment that only a hospital can provide. Get yourself to the emergency room, or if there is no cheaper alternative, call the emergency operator (911 in the United States) for assistance.
If you are confident that you are not an immediate suicide risk; you may not require hospitalization. Nevertheless, you should still seek out professional mental health care for your condition, which is still life-threatening and rather serious. There is a good chance that you are depressed, or may have some other psychiatric disorder that would benefit from proper treatment. You will almost certainly benefit from having a mental health professional with whom you can confide, who can provide you with a more objective third-party perspective on your difficulties, who can help monitor your ongoing suicide risk, and who can help teach you better coping methods than you are presently able to use in addressing your concerns.
You can search for referrals to mental health professionals in your area here.
Even if you start calling for appointments today, it can take time to be seen by psychiatrists and psychotherapists. Appointment schedules may be full for weeks in advance. If this is the case, ask the receptionist if you can have the next available appointment, and to call you if any cancellations occur. It is also a good idea to stress the urgent nature of your need. While you are waiting for an appointment (and between appointments as you require) you can reach out to the various telephone crisis lines such as the ones that are listed on The Samaritans website (www.befrienders.org). In the United States you may also call toll-free 1-800-273-TALK or 1-800-SUICIDE. Teenagers may also call Covenant House's NineLine at 1-800-999-9999. Participating in online support group communities may also be a good idea.