I wouldn't think too much at first and just start putting my thoughts to words. Once you get the monkey off your back by having a rough draft, it is time to logically arrange your write up. Soon, things would start to make sense and you would be done with your second draft. After a gap of few days, read the entire write up and make changes to make it perfect. If you go after perfection in your first try, you will obviously be overwhelmed and wouldn't know where to start.