[fen ""] 1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4 f6
How should I play from here? This move seems to head off the main ideas of my kingside attack; what is the best way to proceed with the plan of quickly developing and attacking?
I think f6 is an uninspiring move. It doesn't force anything, blocks the Knight on g8, and exposes the King.
365chess.com says that Black's win percentage is wretched after f6; in fact it's the weakest reply with Black winning only about 16% of the games.
Good continuations include the trade of Knights in the middle with
...with a pawn-plus advantage to white.
Here's a sample game from 2001, Wolfgang Kuhn is White, Heinrich Lehr is Black. I don't know the strength of these players.
Here is what stockfish sees after a few (note that it is important to wait and allow stockfish to get to at least 20 moves of analysis - it can make a difference).
White to move, suggested Qd3 +1.57