24. 0-0 was the main error I saw. At this point you are in an endgame and the king does not need saftey as it cannot be mated. So you should have played 24. Kd2 Rxa2 25. Ra1 Rb2 26. Rhb2 and he cannot avoid trading his last rook and you clean up the position with the extra rook.
But yes, you have the main idea to trade material when you are up. Very nice game, congratulations and keep up the great chess! 
I think instead of 18. Ne7+, exchanging knights, that 18. Nb6+, winning the Rook, may have been better.
In the endgame, I think 25. f4 (or Re1) would have been a killer. Connected pawns backed by Rooks, attacking a King, would have been unstoppable, especially with Black's Rook stuck on the 2nd rank.
Mony good game! A person had told me that "a mistake is not a mistake unless you recongize it and exploit it". In this game you took full advantage of black many mistakes. You played a hell of a game! I question only one move, 4.Be3 and even c3 suggest by chopra is questionable. In the Opening white has the first move initiative instead of defending d5 with Be4 why not dxe5?
If black take back 4.dxe5 dxe5 5.Qxd8+ Kxd8, now black king can't castle to safety and is expose If 5...Nxd7 6.Nxe5 win a pawn, or 4.dxe5 Nxe5 5.Nxe5 dxe5 6.Qxd8+Kxd8 black king still expose. That's is the normal follow up after playing the aggressive move 3.d4
Was my general policy of exhanging once ahead a bad one? Where could I have pressed home the advantage through an earlier attack from move 17 onwards?
This was my first game on the site, thanks in advance for any guidance.