He'll want to meet for "coffee". After all, that is harmless, isn't it. ("Darling, it was JUST COFFEE with a friend...")

He won't reveal his full name, phone number or address. What's he scared of?

He'll be very sweet and kind, even if you have behaved somewhat nutty. He'll say you're a nice person and wish you a nice life rather than risk incurring your wrath.

He won't show you pictures of his family or family events.

He won't always admit to having children.

His mobile will be switched off at odd times.

He'll tell you everything you want to hear. After all, he has nothing to lose if you're not interested so he can lie as much as necessary to snare you.

He'll make one mistake. Here, you'll need to keep your ears open.

If you know he's married/involved and want to date him anyway, good luck!