Generally, sessions are scheduled weekly especially at the early stages of establishing a therapeutic relationship between the counselor and client.
The intent is for the therapist to gather the necessary history about the client so his or her clinical needs can be properly evaluated and correct diagnosis can be made.  This, in turn, will allow the counselor to develop a custom treatment plan to address the needs of the client.
As the client's condition improves over time, the frequency of sessions may be adjusted to biweekly or monthly as deemed clinically appropriate by the provider.