Castling
Two moves in one: the king leaves the middle and the rook joins the game. Do it early.
You already know how to castle; now, when. The marked squares show the typical situation: the king still in the middle and the rook on h1 doing nothing at all. Castling fixes both at once — the king goes to the corner, far from where the fight happens, and the rook hops to f1, looking down the middle file. It is the best deal in the opening, and the costliest beginner's mistake is putting it off to do “one little thing first”.
You have already developed two pieces. Put the king somewhere safe.
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