+1 to Indefinable Ms. M
I am prior military. I think one thing you may have noticed from us that really are, I would say most of us won't ever even TRY to play it for a discount, so if you are getting someone who is starting off a convo like that, that should be your first red flag.
I wouldn't give up my military ID to anyone that wasn't law enforcement. (it's my first grab when I get pulled over for speeding though lol)
I won't take my DD-214 out of my home unless I require it for something very important. Those are hard to replace from what I understand.
MOS codes are not well known to someone who has not really been in the military, that is a great place to start. tech schools are also job specific, so if you have their MOS code (that's Army) or whatever it is, and where they went to tech school, just ask one of us that was in that branch and we can probably tell you if they are bullshitting or not.
One tip: Occasionally those change. I got into a bar fight one day over ranger school. I told him I went to ranger school at ft jackson, and he hit me thinking I was bullshitting because he didn't know they opened up another school there too.
He only believed me after I whipped his ass, because he didn't want to belive a AG 75F could whip his ass without ranger training. lol.
(Translated: AG means office work, very little physical training, and 75F is basically a computer networking guy), in other words he didn't want to think he could get beat down by a computer nerd.