How to find the best move? (Super easy question, right?)

Okay, obviously it's not an easy question. It's the question every chess player tries to answer. But in all seriousness, what do you do when you reach a position--whether in a game, a puzzle, or a drill--and you're not sure which action to take? Sometimes I find myself staring at the board, not seeing anything. In other words, how do you evaluate a position? I'm aware of the general chess principles (pawn structure, knights vs. bishops, rooks and queens on open files, active endgame king, etc.), but it's obviously more challenging to put those principles into practice. Any tips on increasing visualization/calculation skills? Thank you so much!

@1

"How to find the best move?"
++ That is not even necessary: avoiding bad moves is good enough.

"what do you do when you reach a position"
++ Look at the possible moves and use logic and calculation to eliminate inferior moves.

"staring at the board, not seeing anything"
++ You see several legal moves. Eliminate bad moves and you are left with the good moves.

"how do you evaluate a position?"
++ Look at king safety, material count, endgame if all pieces were exchanged.