I think that it really depends on a number of factors.
How many subjects you want your child to receive help in, how much difficulty your child has in the subject(s), if your child has any special circumstances or learning difficulties to overcome, and what your goals are, are some of the things to consider. Sometimes a child is a very good student, gets As and Bs but a parent just wants to give the child a little extra help, and the ability to ask questions of a different person to get a different viewpoint, and receive help only in that one subject where they get a B in to help the child possibly get all As. Other times a child has great difficulties, needs tutoring in several or all subjects, study skills, and possibly to overcome ADHD, dyslexia, executive function, and other learning difficulties.
The child's attention span needs to be considered. Possibly a session for an hour or two is best, or maybe three or four times for 30 to 45 minutes. Although personally though I think 30 minutes is most often (but not always) to short to accomplish much meaningful results.
I suggest you talk to tutors in your area whose profiles seem to match what you are looking for. A one on one and frank discussion with a tutor can give you some advice suited to your circumstances, your child, and your goals. If what you hear from on tutor seems just what you are looking for that is great, but if not, of if you are not sure contact another tutor for another opinion.
Also, the time commitment and cost as related to the family will need to be thought of. Hopefully you can always find someone suitable in your area within your financial means. You can consider asking for a discount if you are having multiple sessions in a week or longer sessions that save a tutor on travel time. If finances become an issue talk to your school. There might be lower cost or public services they can suggest if your family qualifies. Teachers in the schools also give extra-help for their students after school. This can sometimes be a good supplement to paid tutoring and sometimes is even all that is required. It is more prevalent or popular in middle school and high school but I think is available at all levels.