I have attached a diagram with this post.. 1st go through it and then read the following.. This talks about The Circle of Fifths.. Its very simple technique by which u can easily find out the chord progression in any song.. So just read and Njoi...
There are many purposes for the "The Circle of Fifths":
1. As a guide to figuring out how many flats or sharps there are in a particular key, its key signature.
The key of D has two sharps, and the key of Bb has two flats. Which notes are flatted and sharped in each particular key? If you start at Bb and count in a counter-clockwise fashion, you will get the flats in their proper order. For example, you want to find out which notes are flatted in the key of Eb. Look at the key of F, noting the key of F has one flat, B.
(Note: This is due to Major scales having to meet the W-W-H-W-W-W-H spacing requirement). Starting with B and counting counter-clockwise three places (Eb has three flats,) you end up with the key of Eb with B E and A as flatted notes.
For minor keys simply rotate the outer circle three notches counter-clockwise. You will see that the relative minor key for C is a-minor, for G it's e-minor, etc. The corresponding flats and sharps all apply. I have entered all of these for you as a reference. You still need to get them firmly planted in your mind, as they are an invaluable tool for all aspects of music.
2. Chord Substitution: If you want a substitute chord in any progression, the ones close to it on the circle will be the most logical substitutes. Most songs today move four or five spaces on the circle. One of the most popular substitutions is the "tritone substitution".
A dominant seven chord is unique in that its third and seventh degree can change functions and become the seventh and third of a new chord. The new chord is called a tritone substitution. It is a (flat fifth or sharp fourth) away from the original chord. For example, you are playing a ii-V7-I progression in the key of A, (d minor 7, G Dominant 7 and C Major 7).
Note: You can find all of the ii-V7-I progressions easily by looking at the circle of fifths. Just pick any key and that is the I (Major 7), the next chord to it (clockwise) is the V7 (fifth or Dominant 7), the next to it (clockwise) is the ii (minor 7).
Observing the circle as a clock, look at the circle of fifths six hours away. You will see that from G it is Db, so instead of playing d min 7 to G Dom 7 you play d min 7 to Db Dom 7. It follows that G Dominant 7 has B as its third, F as its seventh and Db Dominant 7 has F as its third and B as its seventh. They both lead to the I chord which is C Maj 7.
Note: Try Substituting the minor 7 chord with the minor 7 chord that is relative to the new dominant chord. For example, you just did a chord substitution for the key of C (d min 7 to Db Dom 7 to C Maj 7), change that to Ab min 7 to Db Dom 7 to C Maj 7. In so doing you are also doing a "tritone substitution" for the ii-7.
3. To determine the best transition or move (modulation) to another key. The closer the two keys or chords are to each other on the circle, the better the chance it will sound as you are moving to it. If you are playing in the key of D (two sharps, F# and C#), the smoothest modulation is to move to either G (one sharp, F#) or A (three sharps, F#, C# and G#). This is due to there being only one note difference between the three keys. That is to say, the key of D has one more note sharped than G, and one less sharped than A.
Most chord progressions move around the circle of fifths in a specific pattern (e.g. D to G to C, etc.). These progressions can move upward in fifths (clockwise) or downward in fourths (counter-clockwise). The chord types (Major, minor, Dominant, Augmented and diminished) in the progression will vary. Try them with songs you already know and analyze them with the circle of fifths so you can see the logic. Then in future applications you can apply what you have learned. Keep practicing and studying!