Cool game with the Evans Gambit; did I play the opening right?

I haven't played the Evans Gambit in a while and decided to try it, although I won did I play the opening right? I checked the analysis and it didn't point out any serious blunders, but I'm just not quite sure what to do in the Evans when the pieces are traded, since its harder to get an attack going(especially my dark square bishop, which usually prevents the black king from castling?

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12 Qa4+ wins the knight.

I think you have a point about wanting to avoid trades. All games in the master database follow 8. Kf1, avoiding trades altogether. I personally like 8. Nbd2: if black trades, you have the bishop pair, and ideas like Ba3 are still available. If black does not take, he is left with a vulnerable bishop on b4, which could be useful for you if you play for instance Qb3 and d5 next. It really doesn't matter that much though: Bd2 was not a bad move, and as tpr pointed out, you had a completely winning position a few moves later.