Keys and Key Signatures
Key Signatures                     got 
you flustered??
No problem!  Understanding a few simple             concepts will have you well on your way to a successful music theory             experience.
Number 1
In determining a key signature for any named major             key, it's important to know whether the key signature has sharps or             flats.  
With the exception of the key of C             major (no sharps or flats) and F major (one flat), any "stand-alone" letter is going to be a major key with             sharps:  G, D, A, E, B, F#, C#.  Of course if a sharp             follows the letter name (F#, C#), the key signature will have             sharps.  If a flat follows the letter name, the key signature             will have flats:  Bb, Eb, Ab, Db, Gb,             Cb.
 
Cb (7)
Number 2
In order to determine the name of a major key that             contains sharps, simply name the note that is a half-step above the             last sharp.  
Above,             the last sharp is D#, so the major key would be E major.
In             order to determine the name of a major key that contains flats,             simply name the next-to-last flat and that will be the key.  Again, the key of F major, with one flat, is the             exception.  
Above,             the next-to-last flat is Ab, which is the name of the major             key.
Number 3
Okay, that works fine if you're given the key             signature, but what if you're given a "tonic note" and             asked to come up with the major key signature?
That's             when you need the info from the table under Number 1.  You must             know whether you're going to be creating a key signature with sharps             or flats.
What should go through your brain if you             are given the following tonic note and asked to provide a major key             signature, or provide accidentals to form a major scale based on             this note?
Is it a major key with sharps or a major key                 with flats?
The note is B-natural, not Bb, so it's                 going to be a major key with sharps!  Coo'.
If I can determine the name of a major key                 signature by going up a half-step from the last sharp,                 then, conversely, I can determine the last sharp by going down a half-step from the tonic note, B.  (... Man, this theory                 stuff isn't as confusing as Burnette is making it out to be.)
It sure is a good thing I memorized the order of                 sharps or I'd be up a creek right about now.
Let's see ... Fat Charlie Goes Down All Escalators Backwards:  F#, C#, G#, D#, A#, E#, B#.
If A# is the last sharp, then the key of B major                 has five sharps:  F#, C#, G#, D#, A#.
Piece of cake, eh?  Now, what if you're given this note?
Okay, this has got to be a major key with                 flats because the note is Db ... duh!
If I can determine the name of a major key                 signature by naming the next-to-last flat, then, conversely, I                 can add one more flat to come up with the number of flats in the                 stinkin' key signature!
It sure is a good thing I know that the order of                 flats is the exactly the same as the order of sharps, but in                 reverse:  Bb, Eb, Ab, Db, Gb,                 Cb, Fb.
So, then, if I add one more flat beyond Db, I'll                 have five flats--Bb, Eb, Ab, Db, Gb, the key signature for Db major.
Number 4
Alright, I've got the key signature stuff down             now--quite a breeze--but this relative major and minor hoopla             still throws me ....
All you've got to do is remember the easy             formula--the relationship between C Major and a             minor.  These two keys share the same key signature, as             do other keys sharing the same relationship.  
C
a
For any given major key, its relative minor key will             lie a minor third (m3) below.  For any given minor key,             its relative major key will lie a minor third above.
If             you are given the major key F# and asked for its relative minor key,             you simply navigate down a minor third, and your answer is d#             minor.  These two keys share the same key signature:  six             sharps.
If you are given the minor key eb and             asked for its relative major key, you simply navigate up a             minor third, and your answer is Gb major.  These two             keys share the same key signature:  six flats.