I get scam DMs about as often as I get real ones, and I'm on my guard when someone new messages me. If you want to DM me for real:

If you talk about my pictures but only in a vague way, and you refuse to add any details about what you see in the pictures, I'm going to see that as a warning sign of a scam. If I ask you to describe something in a picture, don't respond by changing the subject.

If you offer me money but you insist on one specific payment method for sending me the money, I'm going to see that as a warning sign of a scam. If you really want to send me money for some reason, let me pick the way you send it.