There are many ways to go about this. But, the key is answering a few basic questions to get started.
Here is a checklist covering the various overtime exemption categories.
https://helpdesksuites.com/wp-content/uploads/2018/01/Exempt-Non-Exempt-Checklist.pdf
Here is another link to some assessment tools for employee classification: https://helpdesksuites.com/kb/deluxe/comp-assess/
Finally, here is a link to the FLSA guidance on overtime exemptions. https://www.dol.gov/whd/overtime/fs17a_overview.htm
October 2018
Overtime exempt
white collar exemptions
employee classification