Fairly simple. They do a drug test and if you get a security clearance they ask various questions. There are a bunch of requirements but the recruiters are upfront and clear about them.
Interview questions [1]
Question 1
Have you ever done drugs? Do you have any medical conditions?
Meet with recruiter and take ASVAB. After ASVAB, complete MEPS physical and wait for shipment date to begin OSUT at FT. Benning, GA. Upon completion of OSUT, report to duty station and begin term as an infantryman.
It’s a board of members that ask MOS related questions about your job and then they see if you are proficient in that realm. If you are then you will pass the board and get promoted if not you will go back and try again at a later date.