i'm not entirely sure what you mean. i've spent the past 3 months learning how to use and program an Arduino to control steppers, so I can definitely help you.
first off, you should look into the stepper control code we've already written. the easiest to understand is in the GCode_Interpreter firmware. its located here: [
svn.reprap.org]
secondly, what stepper drivers are you using. i would recommend the RRRF stepper motor drivers. they use the industry standard step/direction interface. what this means it that you control them with 2 pins: step and direction. when you send a pulse on the step pin (take pin high for 10 usecs, then back to low) it will take a step in the desired direction. the direction is determined by direction pin. high = forward, low = reverse.
thirdly, there is an algorithm for coordiniated movement along a line (ie. when you want to move in both XY at the same time in a straight line) this is called Bresenhams DDA (digital differential algorithm) it has been implemented in the code above.
thats all there is to it, good luck!