Find an inspiration for your home entertainment center. An image of a piece in a style you like is a good place to begin; furniture catalogs and wood-working magazines are two sources. Get as many views of the piece as possible. If you can, find a plan that is close to the look of your dream furniture and make the adjustments you want.
Draw the entertainment center; sketch it first several times, making changes to refine the design with each sketch. Draw the face, the side, the inside with the doors open and any other angle that will help you understand how the piece goes together. Draw a front and side view on a pad of graph paper at a scale of 1 inch for every 1 foot. This means an entertainment center 6 feet tall in reality will be 6 inches high in your drawing.
Take the furniture piece apart in your mind, drawing each part. Start with the base and feet. Decide exactly how the feet will attach and how the base will be built. Use wood-working plans, books and websites to get inspiration and learn how pieces should fit. Decide how the side panels, back and front frame will attach to the base. Sketch each piece, including dimensions, and then draw them to scale to make sure they fit with each other in the way you want. Make adjustments until every part is correct.
Work your way up the entertainment center, drawing drawers, shelves, hinges and pulls. Draw every detail including the wood trim and any other detail pieces that will be added to the design. Divide drawers into these categories: front, back, side, bottom and drawer face. Draw the fronts and backs of doors and other pieces. Determine exactly where the hardware will attach and how.
Make a final rendering of each section of your furniture, adding dimensions and notes about construction as needed. Writing a description of each step in the construction process will help you work through any problems before you ever cut a piece of lumber.