Take the graphing paper and pencil and create a legend at the bottom of your plans. Example: two graphing squares equal 1 inch.
Begin a rough draft of your subwoofer box. Keep in mind the size and shape of the subwoofers, and the applications you're using it for. You can make a bigger box for live band shows, or make it smaller for the trunk of your car.
Draw two views of the speaker box, both front side and back side. On the back side, remember to leave holes and outlets for electrical cords to attach to the speakers. Keep in mind the type of outer material you're going to use; whether it is paint or carpet, those should all be included in the design.
Take all of the rough draft drawings and finalize them onto one page for your plans, which also should include your building materials and how much you will need of each material. Then, when it's time to go to the store with your finished draft, everything will be included on one sheet.
Go to your nearest wood and hardware store to pick out everything you need. The more materials you have present at the start of the project, the quicker you can get it done.