Every chess player is different. What works for some does not necessarily work for others. There are different reasons why someone may be rated 1400. For example, Player A might be rated 1400 because his opening knowledge is master-level and most of the time he can get a pretty nice advantage out of the opening. Yet Player B might be rated 1400 because he has an unwavering fighting attitude and solid endgame technique. So obviously if both Player A and B asked a teacher, "How can I get to 1500?" The answer should be markedly different. I say all this to preface the statement, this is how I picked up 400 rating points in one year. This is not how I suggest you pick up 400 points.
I was rated USCF 1209 a year ago. This 1209 was not just a slump I was going through either. It was my first official rating after 25 provisionally rated games and was established in October of 2008 right after our 69th State Championships. In all of my provisionally rated games, I never broke 1300. So it's fair to say I was a legitimate 1209 player.
After my rating was established, I finally had a clear idea that I needed to change some things. Both in the method of choosing moves and my actual discipline at the board. Regarding my play over the board, I made the decision to change two things; I had to start using way more clock than I was using, and I was going to play one section higher than I should be. If I was going to lose I wanted to lose to good players who I could learn some things from. Regarding my play, I picked up a study program from GM Jesse Kraii based on Lazlo Polgar's Chess: 5,334 Problems. The first 300 or so problems are mate in one problems that intend to firmly concrete the most basic mating patterns, a fantastic basis for any chess player to build on. The next 4,000 problems are Mate in 2 which combine the basic mating patterns and improve your powers of calculation. I hit this book with gusto. Combined with my decision to play up and use more clock I picked up my first 1300 rating in a month and a half.
After I was rated 1315, I was convinced the Polgar book was exactly what I needed so I hit it harder. I completed the 300 Mate in One problems more than 5 times and did over 700 Mate in Two problems within the next two months. I also completed several micro-game exercises recommended by Michael De La Maza in his book "Rapid Chess Improvement". My favorite was the Knight Sight exercise that trains your mind to both use your knight for some serious harm and how to spot your enemy's knight forks.
My confidence was soaring. By April of 2009, through regular tournament play and an occasional weekend tournament, my rating peaked at 1510. Then I sort of leveled off. From April to July my rating went from 1510 to 1483. During that three month time, I decided the Polgar study plan had taken me as far as it was going to take me for now. I needed a new approach.
I read and completed "The Amatuer's Mind". I learned a vast amount of new chess knowledge in regards to middlegame and positional play. Armed with my new knowledge my rating promptly went from 1483 to 1457 in the next two months. The reason for the decline in my rating was my rethinking of chess. I was relying on new methods instead of the methods that got me to 1500. I still felt like I was playing better chess even if it was not showing in my actual rating.
After the Amatuer's Mind I decided to firm up my openings. I purchased "Chess Openings for White, Explained" and its counterpart for Black. My repertoire is not based exclusively on these recommended lines (for example I tried the symmetrical English as Black and freaking hated it.) Chess Openings for Black recommends exclusively the Hyper-Accelerated Dragon against 1.e4. Against 1.e4 I play e5, c5 and e6 for variety. It also recommends the Nimzo-Indian against 1.d4 and I play the Dutch and the Queen's Gambit Accepted. However, my opening play improved a great bit. These books were directly responsible for 3 wins that I picked up in the last year based on easy (but extremely sound) traps that my opponent walked right into. My rating held steady until August 2009 when I was rated 1479.
I then read and completed "Art of the Middlegame" by Kotov and Keres. In one of the very best chapters in any chess book I've ever read, the Chapter entitled "How to Defend Difficult Positions" totally changed my perspective on the game of chess. For the first time I realized the game is not just a game of wooden pieces and dry analysis. It's a competition between two flesh and blood humans engaged in mental and psychological battle. Aside from the excellent technical lessons learned from this book, this one chapter alone endowed me with a fighting spirit like I've never had before. Armed with a new attitude and the heart of a lion and my previous work throughout the year, my chess play began to gel. I picked up 75 points in one tournament and hit my highest rating ever of 1528.
In our next club tournament I picked up another 40 points and hit 1569. On October 10th 2009, I took my 1569 rating to a weekend tournament out of town. In my first round game I got paired against a guy rated 1703. To give you an example about my change in attitude, I would have ordinarily said to myself "Oh wow, 1703, I'm going to have to play the best game of my life to beat this guy". Instead I sat down across from him and looked at his rating and said to myself, "1703? Wow this is going to be the highest rated opponent I will have ever beaten by the time this game is over." I won. When this tournament was over I was rated 1593.
The next step for me was the 70th South Carolina Championships. This tournament was exactly one year after my 1209 rating was established. I was determined to perform well. My first game I won as black versus a 1400 rated opponent. I had to take an unforseen second-round bye. The third round game I got paired off against a player rated 1350 who I really had to fight hard and wound up with a draw when I was a pawn down. I was very lucky to not lose this game. My fourth round game I beat the same 1700 player as mentioned in the previous paragraph. My final game I defeated a 1650 rated opponent to finish with 4 points out of 5 in the Under 1800 section and a shiny new 1643 rating. My performance was also good enough to be awarded the "2009 South Carolina Amatuer Co-Champion", split with another guy who I never got a chance to play.
My General Advice on Improvement
Obviously I can only speak for players around 1000-1400 on how to improve. However, there is absolutely zero substitute for hard work. You have to enjoy the work you put into chess as much as the games you play. There is no shortcut to get to anywhere that's worth going. Secondly, you have to be a fierce competitor. I love competition and I believe my fighting spirit echoes in my play. Thirdly, you have to have a solid foundation. Pattern recognition, basic tactics and generally active play will take you a long way. Finally, you absolutely cannot be afraid to change. If you notice, two or three times during this article, I said "I realize I needed to change". You absolutely cannot continue to rely on the methods that got you to where you are to get you further. Sometimes you have to tear down your building and rebuild it so it can be taller. Now matter how good of an engineer you have designing your building, your foundation will only take you so far. Never be afraid to destroy your foundation and rebuild it stronger. I believe those resistant to change are the ones who will be stuck in their rating.