If it's an equation, such as y=mx+b, the slope is whatever the value of m is. For example, if the equation was y=2x-4, than the slope would be 2.
When solving this on a graph, choose any 2 whole number points. (preferably close together, because it makes it easier) Count how many lines up/down (the y axis) and how many lines over left/right (the x axis) and put the up/down on the top of a fraction and the left/right on the bottom. for example if up was 2, and right was 3, than it would be 2/3. Down is negative, and to the left is also negative. If there are 2 negatives (one on the top and one on the bottom) than they cancel each other out and become positive. For example: -2/-3 would be the same as 2/3. Hope this helps :)