You want to know how and why? And in relation to ratings... ok. Rating jumps happen because I win games, I guess the how would involve posting the rating formula?
Yeah yeah, I know what you meant 
My skill went up after reading a book or over a period of time taking my games seriously meaning analysis afterwards. Like fiveofswords I don't know how much for sure because I don't go to a lot of tournaments each year.
The full question would be: How did you study to achieve your biggest rating jump and why do you think your study was helpful?
I think Fiveofswords, if I interpret correctly, your rating increased because of your book studying and analysis of perhaps pro games?
And as orangehonda confirms, reading books seem to contribute the most to your skill after around 1400 etc. Before that, it's a matter of tactical intuition development and practice in games. However, I don't think you can simply practice your way to 1900.
For me the biggest improvement took me from about 1700 to 2000uscf. It was a while back, but basically I was doing two things. First I was playing a lot of speed chess much stronger players which gave me numerous chances to experiement with my favorite openings and defenses. Second, I started studying more endgame technique and little of anything else. I found that by having learned some important concepts about advantages in endgames that I could sometimes broaded my approach in a game by finding/looking for ways of bailing out of an attack or some such into a favorable ending that I'd not been aware of before. Knowing what to look for when heading into "simpler" positions can add a lot of point to your score table.
The thing with rating jumps is that they're different for everyone. The way I think of it is they happen when you fix the critical weakness/weakest link in your ability or understanding that was effectively holding you back. Lets say the rest of your game is at a 2000 level, but there's one or two things that keep you back 2,3,4 hundred points -- after you fix it then boom.
If it happened that a person 1500 in every respect jumped to eg 2000 it would be odd to me but I'm sure that's possible too.
As a novice trying to deal with tactics I would try to figure out my opponent's last move by looking at the squares it no longer defended, what it newly attacked, and where it could now attack in the future. Also early on I was told there was such a thing as weak squares/diagonal (which I didn't understand but I'd heard of) so an epiphany like fiveofswords had I probably wouldn't have had.
For me I think I had a rating jump when playing at a club where everyone was about 200 points higher than me and one day I started asking myself "do I like this move for my position no matter what move my opponent plays?" and I began having nights where I broke even -- and I'm sure many people hundreds of points below me already ask that, so for them it's different still.
I think a sure shot is reading books and playing in tournaments (with improvement in mind). Just work your way though a book, cover to cover, one at a time. It doesn't have to be quickly, even just one or two a year. Also go to tournaments or a strong (people better than you) club and one day you'll wake up at 2200, I believe this.
I've had my biggest jump in rating( as others not sure becouse dind't played many tournameents) when I read the book "matter of teqnique"(don't know if my translation from italian is good lol), I had it not easyly after reading the book and taking his ideas, think wich was hard for me becouse it was a book way out of my ability, but after playing. In fact the book gave me the important concept of weaknesses wich I hadn't before, so all the positions I saw I was finally seeing the weaknesses and at the start it was counterproductive too! I was seeing weaknesses but over-valuing them! So the jump was actually on a month time period when I were able to actually use weaknesses well.
the funny think is that I've now problems understanding where to value more dinamy or weaknesses
For me the biggest rating jump I had was from 2000 to 2300 in bullet / blitz chess.
I play as "pinnoy" in most chess playing sites, including chess cube.
For a long while, I was hovering below 2000. 2000 was my "Elo-Wall". When I surpassed 2000, I realized that it was not so difficult to go over 2100, 2200, 2300. It was harder to go over 2000 than to go over 2100 (after my jump)
What I needed back then was a "spark-plug" of inspiration...and that came when I 'solved' my opening problems as Black vs 1.e4
I read a little known article on the Czech Pirc, used by Kasparov to draw effortlessly vs Deep Blue.
That one game and the annotations had an enourmous impact on me. After that I felt to recharched and so confident that I instantly jumped to 2100 in no time. The resulting positions from the Czech Pirc were so 'familiarly easy' to me that soon I sped up my playing rate as well as Black. I would play 10-15 moves almost instantaneously. Of course I did a little homework. I studied the Czech Pirc (I didn't know it even had a name). That and my initial burst of inspiration proved to be effective in my rating jump.
To others, it might be some other form. I would imagine discovering an 'antidote' to your fears playing the sicilian, or learning deeply a line in the ruy, it doesn't matter what.... but the effects would be the same.
Now I have a new wall of 2400. I need another spark! I can't get past 2400 yet..but I think in time it will come.
Yeah, I have to study my books first before I have any "jump" in ratings, otherwise I'm just using the same bad habits/mistakes/problems in my gameplay and playing at only a <1600 level.
It seems your idea that black openings should be studied extensively might help. With black I play responsively, I respond to the opponents opening and try to make some sort of counter attack. However, if I knew an opening well enough maybe I'd be better at defending with black.
For me the biggest rating jump I had was from 2000 to 2300 in bullet / blitz chess.
I play as "pinnoy" in most chess playing sites, including chess cube.
For a long while, I was hovering below 2000. 2000 was my "Elo-Wall". When I surpassed 2000, I realized that it was not so difficult to go over 2100, 2200, 2300. It was harder to go over 2000 than to go over 2100 (after my jump)
What I needed back then was a "spark-plug" of inspiration...and that came when I 'solved' my opening problems as Black vs 1.e4
I read a little known article on the Czech Pirc, used by Kasparov to draw effortlessly vs Deep Blue.
That one game and the annotations had an enourmous impact on me. After that I felt to recharched and so confident that I instantly jumped to 2100 in no time. The resulting positions from the Czech Pirc were so 'familiarly easy' to me that soon I sped up my playing rate as well as Black. I would play 10-15 moves almost instantaneously. Of course I did a little homework. I studied the Czech Pirc (I didn't know it even had a name). That and my initial burst of inspiration proved to be effective in my rating jump.
To others, it might be some other form. I would imagine discovering an 'antidote' to your fears playing the sicilian, or learning deeply a line in the ruy, it doesn't matter what.... but the effects would be the same.
Now I have a new wall of 2400. I need another spark! I can't get past 2400 yet..but I think in time it will come.
2012 Update. I have finally crossed the 2400 bullet chess border last 2011 and now I have crossed the 2500 border. Hopefully I will cross 2600 next time!
My biggest rating jumps have come when I actually have been able to play in tournaments and let my rating catch up with my ability.
Other than that, there hasn't been any one thing that helped me get better. I subscribe to the "The secret to chess is that there are no secrets" theory. I just do a lot of things to try to get better, and over the long haul the work steadily pays off.
my biggest jump was 1983 at the dallas chess club but i went in unrated
Update:
I have now crossed 2600 in online chess and have maxed at 2645.
One of the main contributors of my rating jump is my increased knowledge in my favorite defense, the Czech Pirc variation, and enhanced confidence playing against anyone. I used to fumble around in the middlegame especially when facing tougher higher rated opponents. After hundreds and thousands of online games this irrational fear gradually subsided. I noticed you will begin to play markedly better when you have confidence. The moment I realized that these 2400-2700 'beasts' are human after all, I started winning against them too.
My USCF rating had been about 2050 for a while but then beat a former Illinois Champion in city to city unrated games. Also had held my own against another former Illinois champion. [unrated home games]
Also drew a 6 game home match vs a very tough master-- he had won the Chicago Open with a score of 5 wins and no losses or draws.
So one year [1973] decided to play in the US Open in Chicago. For the whole year [15 games] my performance rating was 2439.
It was the confidence gained from those unrated games vs three tough masters. Just decided to give no quarter and play for a win even against the highest rated opponents. [ was no longer playing scared]
From 700 to 1100 by overcoming the pool of number-named accounts created less than one month ago. Think "magnus123" created last week making basic blunders and suddenly playing at 99% accuracy in end game...
I was just wondering your own personal story on how you achieved your biggest rating jump or steady increase over a relatively short period of time (it doesn't have to be instant).
Was it a book that you read? A lesson you took from a master? Was it gradual after thousands of games?
For me, my biggest rating jump between ~1300->~1600 was through reading articles daily on chess.com and mainly using Tactics Trainer constantly (I think this really made a difference, before I would fluctuate between TT ratings of 1200-1400, and then after a while, I could see the better moves in time!)
Now I hope that by purchasing my first chess books recently, and learning more about positional play by watching videos, and trying to find a good training schedule, I hope I'll make my next jump.
Maybe your story will help someone.