Pescador's advice about practicing in good visibility is key. Get used to distances off of major features in your area and remember them. Learn how to use your radar's features like VRM, EBL, and or parallel index lines. Read up on the difference between true and relative vectors if using trails or plotting other vessels. You want to get to the point where using your radar becomes second nature. Trying to figure out what you're looking at once already in the fog is a tactical error.