I've played chess informally with family all my life, but never with ratings or specific openings, and I never studied any chess theory. Only recently (in the past week) have I started reading about openings, tactics, defenses, etc. I have started practicing against Sigma Chess at a rating of 1200, and it has been destroying me. However, this morning I was able to scrape a win together! It's my first victory at this level, and I'd appreciate all the criticism I can get. 

Move 17. a5 really bothered me, so I went back and undid all the moves after that point to see what would have happened if I had gone straight to Qg6. It still ends up a win for me, but...I felt very sloppy as I was finishing this game. I think maybe my endgame needs a ton of practice and I probably missed a million chances to end the game earlier. I just could not seem to pin down the black king.

Thanks Joey. Next time get the knight to C3 instead of fooling around with pawns, and I shouldn't count on black making stupid choices when trying to stop the mate with Qh5. I know a5 was a terrible move. There are two things I don't understand though:

If Qa5 was not the right way to start off an attack against the king, how should I have gone about it?

And, I think Re1 helped me later on. You don't think? I know I gave black a move instead of keeping the king in check, but I was fairly certain he would take my rook and I'd keep the check open. I wanted my rook free of that little prison to make use of the open e file. How could I have done this differently?  

You're right. I rewound the game and forced the computer to move Ne5 and played it out. It went terribly. 

Alright. I'm enjoying the criticism on this game, so I've taken Joey's advice and I've gone back to move 10 where I moved to b3 instead of Nc3. This time, I took Nc3 instead, which prompted Black to play Qxb2 and changed the game around. I also took his advice with dxe5 instead of bxe5. Here is the result, and yes I am ready for another round of tearing me a new one for my mistakes:

After Black played Qxb2, 11.Nb5 would have been more fun.

15.Na4 looks to be a blunder that Black didn't take advantage of, the Knight on d4 was going begging.