Transposing is really quite straight forward......it's basic math. Let's start with the simple notes/chords
A B C D E F G and assign numbers to them 1 2 3 4 5 6 7
Any adjustment you make must be made evenly across all notes/chords.
For example, a basic 12-Bar blues progression using A - D - E (you may have heard this referred to as a "1-4-5" and never knew why.....the answer is above). In this example, A=1, D=4, E=5.
Now, let's say we wanted to change to C
(The font is uneven, so it doesn't line up right. Paste it into notedpad using Courier)
From this you can see that staying with 1-4-5, you are now using C-F-G....
It gets a little more complicated though.....let's say that we wanted to go to B
no problem, right B=1,E=4,F=5, try it.....something's not right. F is not in the key of B......you have to sharp it....B=1,E=4,F#=5
Do a google search on "Circle Of 5ths" to get to the next step.