When Would You Advise A Friend To See A Psychotherapist?

If it was apparent to me that he/she may be a danger to themselves or others...♥nassy

I would advise any friend to see a psychotherapist/therapist/psychologist if they were having personal problems that were interfering with their life.

I am counseling psychologist, but answer from the perspective of friend in this case, as well.  I would advise my friend to see a psychologist or counselor when:
1) When I recognize that a behavior, habit or action is substantially harming the person or his/her ability to function from previous levels--or having that affect on his/her loved ones.  Usually that would include being unable to function in a productive fashion in the everyday--or being unable to perform formerly routine tasks without incurring great stress/anxiety.  2)  When the friend asks me about what to do about a mental/emotional crisis or issue that is beyond his/her expertise, beyond the ken of other resources, and beyond my own in the role of friend  3) When there is threat of imminent danger to my friend because of the issue, or represents imminent potential danger to others  4)  When the law or ethical code would require me to (court ordered or moral obligation)   5) When the friend has exhausted other resources or tried them without success, and is asking me for other alternatives and ideas  6)When the friend is obviously psychotic or destructive

There are several main broad systems of psychotherapy:

• Psychoanalysis
  - the first practice to be called a psychotherapy. It encourages the
  verbalization of all the patient's thoughts, including free
  associations, fantasies, and dreams, from which the analyst formulates
  the nature of the unconscious conflicts which are causing the patient's
  symptoms and character problems.
• Cognitive Behavioral - generally seeks to by different methodologies
  identify and transcend maladaptive cognitions, appraisal, beliefs and
  reactions with the aim of influencing destructive negative emotions and
  problematic dysfunctional behaviors.
• Psychodynamic
  - is a form of depth psychology, the primary focus of which is to
  reveal the unconscious content of a client's psyche in an effort to
  alleviate psychic tension. Although it has its roots in psychoanalysis,
  psychodynamic therapy tends to be briefer and less intensive than
  traditional psychoanalysis.
• Existential
  - is based on the existential belief that human beings are alone in the
  world. This aloneness leads to feelings of meaninglessness which can be
  overcome only by creating one's own values and meanings.
• Humanistic
  - emerged in reaction to both behaviorism and psychoanalysis and is
  therefore known as the Third Force in the development of psychology. It
  is explicitly concerned with the human context of the development of
  the individual with an emphasis on subjective meaning, a rejection of
  determinism, and a concern for positive growth rather than pathology.
  It posits an inherent human capacity to maximise potential, 'the
  self-actualing tendency'. The task of Humanistic therapy is to create a
  relational environment where this tendency might flourish.
• Brief therapy
  - is an umbrella term for a variety of approaches to psychotherapy. It
  differs from other schools of therapy in that it emphasizes (1) a focus
  on a specific problem and (2) direct intervention. It is solution-based
  rather than problem-oriented. It is less concerned with how a problem
  arose than with the current factors sustaining it and preventing change.
• Systemic Therapy
  - seeks to address people not at an individual level, as is often the
  focus of other forms of therapy, but as people in relationship, dealing
  with the interactions of groups, their patterns and dynamics (includes family therapy & marriage counseling).

There are dozens of approaches, which continue to be developed
around the wide variety of theoretical backgrounds. Many practitioners
use several approaches in their work and alter their approach based on
client need.I hope this helps =)

If you are asking than go with your gut. I have one friend who attempted suicide and recently a relative who did it.  If you think your friend is headed that way, don't hesitate to give them support