What mistakes did I make?

I recently played an unrated game with a friend of mine. At one point he said I should be able to demolish him, but he wasn't going to resign since I usally like playing untill the end. He ended up demolishing me. I did see a couple of mistakes that i made, but as a novice player I am sure I made other ones that I missed?

Move 3 you should have lost a piece since he should have played (pawn) c6.

If by move #3 you are losing a piece then that really shows a lack of understanding the opening.

So I would start with some basic opening principle training first.

I agree with immortalgamer but on move 9 you should have played bxn instead of bxr its totally better to be up a piece than be up the exchange. And moves like 3,4,13, 14, 15,16,17,20,23,24 are either pointless, bad postionally, or loses materially. Try to avoid getting two pieces forked like on move 3, or to run your pieces around, try and formulate a plan and dont keep your king uncastled and get pieces pinned that way. I hope that helped ^_^

Analyzing your games after they are completed is a great way to learn from your mistakes and improve your game.  To find simple tactical oversights, though, the best way is analysis with computer.  There's some facility built into the site here, at least for premium members, but you can also do it yourself by setting up Winboard with Crafty or some other chess engine.  You'll find a lot of mistakes that way, it can be quite humbling.

First of all, I think learning some basic opening principles would help.

You were winning in the early phase of the game, so you should have just simplified into a winning endgame. Also, don't complicate things too much.

Also, you kept leaving pieces where the opponents could capture so you should always see what the opponent can do before you make the move!

Right now, just practice tactics and learn some basic guidelines and fundamentals. A good book on tactics at this level might be "Chess Tactics For Students" by John Bain and after that, read "Back to Basics:Tactics" by Dan Heisman. Hope this helps!

The thing you're suffering from the most is blunders... so 1. take your time thinking out each move, ex. well my knight attacks the queen if it goes here, but then they can take my knight... and 2. Practice! As you play more and more, you will make fewer and fewer careless mistakes.

You (and your opponent) are making a lot of tactical blunders.

On move 23, you could have played Qc8+, and checkmate him -- he can only put his queen and rook between the queen and his king, but you take them and then it's checkmate.

Similarly, on move 25, he captures your queen and you say "I don't get how I missed that." Well, he could have played Nxb2 checkmate!

If you are missing multiple checkmates in one and giving away queens and pieces all over the place, opening knowledge won't help a bit.

Take your time, always do a full blunder check before you move -- as a _minimum_ check all the captures and checks your opponent can do, and for yourself as well.