Ok, here's something very basic but it should help you find your own lick.
Normally, when you do a key change, the procedure is to go I V I in the current key and then two more chords. The V chord of the next key and the root chord of the next key.
In the example below, you go I V I (G D G) and then to the chord that suggests the key change. The suggestive chord is E7 because it resolves naturally to A - which is where you wanted to to.
If we had wanted to modulate to Ab, then we would have stuck an Eb7 in there.
To change to the key of F, you'd put in a C chord of some kind. The passing chord is always the V chord of the next key.
G | | | D | | |
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|------------------------3-------|--------------------------------|
|----------------3---------------|5-------3-------3D------3C------|
|--------3-----------------------|5A------3A------3---------------|
|3-------------------------------|------------------------3B------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
G | | | E7 | | |
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|3-------------------------------|5/--5D------------------5/D-----|
|------------------------3-------|--------------------------------|
|3---------------3---3B----------|5B--------------5B--------------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
|--------------------------------|--------------------------------|
A | | |
|--------------------------------|
|--------------------------------|
|--------------------------------|
|5-------------------------------|
|--------------------------------|
|5-------------------------------|
|--------------------------------|
|--------------------------------|
|--------------------------------|
|--------------------------------|
------------------
Gary Shepherd
Carter D-10
www.16tracks.com