Applications: You should have a template that the user can fill in as an application. You should get the user to send it to you via a Private Message. You may want the user include their name, age and position that they are applying for, also any past experience they may of had and any extra notes the user may want to add. You should also add requirements for users to apply. For example, one of your requirements could be that you must be a member of the forum for atleast one month. You should keep their application for future hiring periods, and tell the user they could be contacted later down the line. This is very effective, because if one of your current staff members resigns or gets fired, you can hire another member far quicker than normal.
Picking the staff yourself: You should see what past experiences the user has before hiring them onto the staff team. You could possibly speak to the previous owners that hired them in the past, and see what they think of the user. You could also pick the user based on their attitude, activity and contribution to the site. You could have requirements for members to be considered for the team but this could be a general rule in your mind when picking the staff members.
I think I have covered enough regarding picking staff members. Remember to consider some of the tips that I have mentioned, and use them for when you are picking staff members. Thank you for reading this article and I wish you luck on finding the perfect staff member for your forum! I hope this article benefits you and your forum.