So, besides the whole "not our job to diagnose a seizure thing", there are several things I consider, IMO. I generally actually lay hands on and physically assess my seizures quickly while I get my stuff ready in case I'm wrong.

Neurologically- I look for eye deviation, nystagmus, and abnormal pupillary reaction (eg, anisocoria or mydriasis). People faking don't usually exhibit these. I also can check reflexes and pain response (eg, plantar reflexes- which I find more telling). I avoid doing things like hand drops or anything that will embarrass or harm the patient, even if they're being a dick.

Respiratory- a pt in full body seizure won't have regular deep breaths, nor will they respond if I ask them to. Nor will they try to hold their breath if I'm assessing. I use my stethoscope in a pronounced way to check this.

Some "tests" I do depend on the circumstance. If the patient has mental health issues, sometimes I direct them or even "talk" them out of it. I've also whispered in their ear if it looks situational (eg, in class, in public, etc) and let them know when they're out of view so they can stop. This actually works for me more than it should.

Other times, if it's mental health or another driver, it could fall under PNES (Psychogenic Non-Epileptic Seizures), and they still need treatment. Under acute circumstances, it's the same as an epileptic seizure, which is a benzo- though usually low dose, usually for anxiolytic effects. So, if this is what I suspect, I still give a benzo as it's still usually doing good for the patient and gives them time and space to calm enough and break their cycle. If anyone has other tips or tricks (or corrections on my thoughts), please let me know. I love to learn.