I line up the marks on each side until I get close enough that the next set of marks is too tight. From that point I begin to turn each adjuster 1/4 turn at a time until I reach the tension I want. Then I'll check sprocket alignment just for kicks, but this method proves pretty true when both adjusters are turned the same number of (1/4) turns past the same reference mark.
i.e. turn one side a 1/4 turn, turn the other side 1/4 turn, check tension, repeat as necessary, then verify sprocket alignment with a straight edge or a string (my method).
EZPZ