The following guitar capo chart can be used to help in transposition of key when playing the guitar with a capo.
To use, take this example, when you are playing an A chord shape, if the capo is placed on the 1st fret, then the chord you hear will actually be a B flat, if you move the capo further up the fret board to the 3rd fret, the pitch gets higher and so does the chord, in this case you will hear a C chord.
If you have a quick release Capo, like the Kyser and so on, I suggest experimenting to see exactly how the chart will help you. E.g. Play an A Chord without the Capo, then play a C Chord without the Capo. Put the Capo on the 3rd fret and play an A Chord, It will hear that it will have been transposed to a C.
I have created a printable landscape orientated version of the capo chart for download in PDF format. Download Printable Capo Chart