I have a strict rule that I must touch my keys before closing the front door, because I discovered the keys in my memory don't open the door as well as the keys in my pocket.
Bonus, when you get into a good enough habit of doing this, you even do it automatically when you're drunk.
These days I just tap my pockets. I freak out if I do that check when I happen to be holding onto my phone or keys
Same thing with my glasses, either they're in my bag, or on my face.
Has served me very well so far.
I live alone, so there is no one else using the same technique who I could deadlock (pun intended).
I do not push the key all the way in. Pushing it all the way in could prevent someone else unlocking the door from the outside.
Same when exiting my car, I make sure I have my keys in my hand when I close the door (I don't have remote locking).
It drives me nuts, because I'm really not that worried about it, I just want to be able to check that I didn't leave it somewhere.