If you're not told specifically which form of a linear equation to use, use whichever you like. Yep, seriously. If you're asked to graph an equation in standard form but you like point-slope better, you can turn the equation into point-slope form and then graph it. If you're asked to figure out an equation from a graph and not told how, do it however you like. Different forms make sense to different people. If we're not mistaken, you're a very different person.