There are many important considerations to weigh when 

choosing a therapist.  There are two very useful pamphlets 

published by the American Psychological Association.  They are: 

A Mental Health Patient's Bill of Rights, and, Change 

Your Mind About Mental Health.

One obvious consideration when choosing a therapist is 

gender: do you have a preference for a male or a female 

therapist?  For many people, the gender of the therapist is of little 

concern.  For others, this is a very important consideration. While 

many women assume they will feel more comfortable talking to 

another woman, it is important to consider the benefit of 

developing a healthy therapeutic relationship with a supportive, 

accepting, nurturing male. Experiencing the safety of such a 

relationship, in which appropriate boundaries are clearly defined 

and respected, can help a woman redefine and establish more 

healthy relationships with men in other areas of their lives.

For heterosexual couples choosing a marriage counselor, one

fact to consider is that there will be either two women and one 

man, or two men and one woman in the therapists' office during 

counseling.  This should not make a difference to the progress of 

the marriage counseling, but may affect the perception of 

counseling during the first few sessions.  

Especially if one of the partners in the couple does not really 

want to go to marriage counseling, that person's perception might 

be that they are being "ganged up on."  This "two against one" 

perception can be overcome if the therapist is the same gender as 

that person.

This is not usually a problem, and when it is, it is commonly 

experienced during the first few sessions only, until trust can be 

established, and a familiarity with the process, and with the 

therapist, can be gained.

http://www.apa.org/pubinfo/rights/rights.html