Section 4.B.(iv) of the EULA says third-party programs can't connect to the WoW client or service. I take this to mean that third-party programs can only send input to WoW by doing the same things as a user: pressing keys, pressing mouse buttons, and moving the mouse cursor.

(However there's at least one programmer here who disagrees with me. If I understand him he thinks it's okay to hook DLLs.)

So my answer to all questions of this type is that your program is supposed to do it by pressing keys, pressing mouse buttons, and moving the mouse cursor. You don't need any special advice for that. Just watch your fingers when you play the game normally and wherever possible, make your program do the same thing.