To more easily graph this, convert it to slope-intercept form (y = mx + b, where m is the slope and b is the y-intercept):
x - y = 1
-y = -x + 1
y = x - 1
The slope is 1 and the y-intercept is -1. To graph this, plot the point (0, -1) and count 1 unit down and 1 unit to the right. Do this once more, connect the points, and you have your line.
Hope this helps.
