Unfortunatly the button isn't working here yet. What's the general rule of thumb or any guidelines on adjusting these ,if there is any?

 

drop a line from the middle of the fender flare straight down mesure from tire to the line.

Ideally you want the same distance each side.

...unfortunately this wont work under all circumstances due to shotty factory tolerances and the unknown history of the car.

You could you a variety of other reference points though.

Measure with the car on the ground, but you probably wont be able to adjust it unless lifted....Its pretty common sense

 

start with the length on the stock one and you will be pretty close. Tune from there.