We all have our specific planning strategies before we right. Some of us have changed them over time and some have kept their same process since the time we learned what a 5 paragraph essay was. The point is that a planning process is important. It helps you weed out the fluff that weighs down your writing. Whether you write an entire draft and then go back and edit or you strategically outline every detail before you write, it does not matter as long as you have a process that makes you successful.
Personally, I find that writing one whole draft and then going back and editing work for me. I tend to just let my mind flow onto the page and clean it up later. For those of you that may struggle with finding your writing process, here is a basic outline from Purdue Owl.