A different topic very similar to this used the same word "best."
There is no best, otherwise chess would be boring.
Anyway, there a few different thing that can happen from there like a four knights or a vienna. Most games you'll be able to play 2...Nf6 3...Bc5 4...d6 5...0-0 for a fine game.
Probably more important to be comfortable with the various pawn structures that may arise so you can find good places for your pieces. For example sometimes white may want c3 for a pawn (to support d4) or for the knight (keeping the pawn on c2). Sometimes white may play f4 in vienna style, or again block with a knight, Nf3.
What is the best defense against the Bishop's Opening (1. e4, e5 2. Bc4)?