First learn your basic mating patterns.
King + Queen vs. King
King + Rook vs. King
King + 2 Bishops vs. King
King + Knight + Bishop vs. King.
You'd be amazed how many intermediate players don't know that last one. To improve it is imperative that you can perform all of these mates efficiently. In learning them you'll learn about fencing the enemy King and the principle of opposition.
Next move to King and Pawn end games. Learn how the principle of the opposition determines whether the side with the extra pawn can win or must settle for the draw.
Then King + Pawn vs. King + Queen. Surprisingly if the pawn is on the seventh rank and in the bishop or rook files the side with just the pawn can force a draw. Learn why.
Build from there. King and Pawn end games - rule of the square, King and rook endings. By understanding how the game ends you are better equipped to play the game as a whole. When I teach chess, I teach it backwards for this reason.
It's easier (and less overwhelming) to learn how to maneuver with only a few pieces on the board. Once you master those situations controlling the whole army from the start will be less of a chore.
I know a little of what I'm talking about (ELO rating 1750)
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