when should you promote your pawn into a knight


That's one of the ideas behind blitz and bullet.
Its also one of the ideas behind chess ratings too.
heres a puzzle an underpromotion puzzle i made
why must you promote to a rook?
Took me about 20 seconds to see why.
But whatever the length of time - nobody is going to understand the why of that problem unless 1) they spot black's pawn at d2 at the bottom of the board in post #13 here ... and 2) they start thinking about that pawn and what its presence on the board means
Nobody will ever think about something unless they start thinking about that something !!
I looked at a knight promotion as well, but then there's the a4 escape square (and promotion of Black's pawn is also not forced).
If white promotes to a queen, black will to and after queen takes queen, it is stalemate. Anything else than promoting to a rook/queen looses
I meant that if White promotes to a knight. Black has the option of escaping via a4.

When playing I realized you could turn a pawn into any peice including a knight when is turning a pawn into a knight better than turning it into a queen
When it’s the best move

Yes - that's what I was thinking. That the c5 pawn must be taken first.
Its almost like an 'Occam's Razor' in chess - to consider that first.
There's something else - called 'knight in phase'.
Black's knight needs to be on a black square anytime white's Queen is on a1.
And the good news is - once the knight - to - be that is the h-pawn makes the single pawn move - then that's guaranteed I believe.
The idea of 'knight in phase' comes up in a lot of endgames.
Like with a King locked in the corner in front of its a-pawn or h-pawn that it wants to promote with the other King toggling on two squares to preserve the draw against a knight.
If the knight can check that King - then that knight can only draw.
Its 'out of phase'.
If its a bishop - then its easy. You just slide the bish one square or so on the diagonal ... and the lone king has to back off and let the other king out.