King and queen is lesson 2 of 3 in Basic checkmates, a checkmate course suited to players rated around 550 (complete beginners). The queen can't mate alone, but with her king's help it is easy, if you avoid stalemate. It has 3 interactive exercises: 2 find-the-move puzzles, 1 exercise playing out a mate. You play every move on a board and get feedback straight away. The lesson is free.
What this lesson explains
Use the queen as a fence: a knight's jump away from the enemy king, she shrinks its box without giving check. Make the box smaller, then walk your own king up and mate together. Always leave the enemy king a square to move to, or it is stalemate.
What you practise
Checkmate in one.
Checkmate in one, and do not stalemate!
Now the whole thing: checkmate with king and queen.
chessGM