It's a simple fact: people who are happier in their environment are more productive workers. According to the Harvard Business Review, the level of worker's happiness affects worker's productivity, creativity, and commitment. Writers may work in their own home environment instead of in an office cubicle, but the same concept applies. If you make your work environment more pleasant and user-friendly, your word count and quality of work will likely increase.
You need some quiet and privacy
The writer who works at home faces constant interruptions all day long if they have a family in their house. The best way to avoid the worst of these interruptions is to create an office environment with a door that closes. Closing a door signifies that work is being done, and that the writer isn't available for casual conversations and random interruptions. If a separate office isn't available, a corner in a bedroom is better than sitting at the dining room table.
Comfortable equipment and good ergonomics
Your office environment is one you'll be living with for hours on end, so it needs to be a comfortable one. Choose a desk that's large enough to allow you to spread out with notes, books, coffee cups, and any other small items important to your work. Spend the extra money to get an ergonomic office chair with lumbar supports. Your back will thank you. Move your monitor up, if you work on a desktop computer, so that the top of the screen is a few inches above eyeball level when you're sitting up straight. Consider a split keyboard, and try out a number of models in the store before you settle on one to take home.
Acquire the best tools you can afford
Get the best computer you can afford, and use the type that is most comfortable for you, be it laptop, desktop, Mac or PC. A good printer is necessary, and those that scan and upload as well as print can be had for not much more money. Choose a good set of speakers and a very comfortable mouse, and consider wireless versions for less cordage chaos. A wrist rest will help to prevent carpal tunnel syndrome or tired hands, and a soft mousepad will cushion your hand all day long.
Optimize the look, feel and sound of your writing-space
You can put everything you need into a room and it will still look like a sterile cube. What's the point of getting to work at home if you don't get to enjoy it while you're there? Paint the walls a great color, and put up posters of your favorite books or works of art. Lay down an area rug to add color and mark the confines of your office area. Find great ambient sound, Motown music, or whatever motivates you to work. Install a mini fridge to keep your bottled water or sodas cold, and add that all-important coffee maker for a crucial jolt of caffeine. Light some incense or a candle, do whatever you can to make for a comfortable environment.
Keep the Faith and may the Force be with You