If you go into the world of warcraft game, and press escape, you get to the menu.
One of the options is keybindings.
Click on this.

Scroll down quite a ways, and you have the option for various bars.
BottomLeftBar, BottomRightBar, RightBar1, RightBar2 or some such.
The default bar has the keybinds 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, -, =.
The other bars don't have default keybinds, but you can add keybinds to any of these.

In general, if you're right handed, you want your right hand on the mouse.
Which means you want to use keys which are easy to reach with the left hand.
These are the prime keys for keybinds, for a right handed user.
~, 1, 2, 3, 4, 5, 6
Q, W, E, R, T
A, S, D, F, G
Z, X, C, V, B

In addition to this, you can easily reach the left Shift and left Control buttons with your pinky finger.
And the left Alt button with your thumb.

So take an unused bar button, and hotkey it to one of these keys.
Then create a macro, and drag it to a key, which you have keybound.