The scotch has quickly become my favorite opening, but rarely goes the way I intend initially. What other ways are there to gain an advantage if, for example, black attacks the e4 pawn rather than defending e5?
"What other ways are there to gain an advantage" ++ You cannot really gain an advantage. White is up a tempo, but that is no real advantage. If you play 1 e4 e5 2 Nf3 Nc6 3 d4, then it is logical to play 1 e4 c5 2 Nf3 d6/Nc6/e6 3 d4 1 e4 e6 2 d4 d5 3 Nc3 1 e4 c6 2 d4 d5 3 Nc3