A good well-rounded hamstring program should be part of your workout and performed two to three times a week. The number of individual workouts you want to include in the hamstring program will be determined largely by the type of split you wish to do.
If you are going to perform a full body type split, your hamstring program will likely be performed three times a week. In this format you will target every muscle in your body in a single session, give a day to rest and then hit it again the next day. This works best for those wanting to work out on a Monday, Wednesday, Friday type of schedule.
A second option would be to split the body up into lower and upper body workouts. If this is what you would like to do then you will likely perform your exercise selection for this muscle group twice per week, occurring on the lower body days. Individuals who are doing this format can either perform slightly more exercises or sets per workout as they will have less volume in terms of muscle groups to cover (as opposed to someone on a full-body program). Just be sure that you perform this set-up in a fashion such as:
Monday - Upper body
Tuesday - Lower Body
Wednesday - Off
Thursday - Upper Body
Friday - Lower Body
Weekend - Off
This will ensure that you are providing enough rest in between sessions. You could certainly switch around the Thursday and Friday workout in the above example or alternatively move the lower body workout on Friday to a day on the weekend. As long as you are getting at least one day in between sessions for each muscle you shouldn't have too much to worry about.
Finally make sure you also perform some good quality stretching exercises with your workout to create a balanced routine.