1. Keep the weight of your arms supported, by either a chair with arm rests, or by letting your forearms rest on the desk. If they are not supported, your shoulders and neck are doing some heavy lifting, when they could be taking some much needed rest. Also make sure your keyboard and mouse are not too far away from you, causing you to reach.
2. Keep your head back! Your ear should be in line with your shoulder, most people have what is called anterior head carriage. This is where your head is a in front of your shoulders just a little too far, and causes some serious strain on your neck. Practice chin tucking exercises every day to start bringing your head to a natural resting place, and make sure to not crane forward when staring at that spread sheet for hours.
3. Sit up! If you scoot your chair closer to your desk, it will help you to avoid slouching.
4. Have your monitor directly in front of you, with the top of the screen at eye level. Make sure your computer is not off to one side of your desk, causing you to constantly rotate your head one way all day long.
5. Sit to stand desks are great for your body! You can stand and take the stress off your low back, or sit when you hit that 2 pm wall. 
6. Maintain good neck posture. If you have a job that requires you to be on the phone frequently through out the day, invest in a bluetooth head set. Not only will this keep your arm from getting tired, but it frees up your hands to type or write. Holding the phone between your ear and shoulder is the opposite of good neck posture. 
7. Get up and move! Set an alarm for each hour, this reminds you to get up and go fill your water bottle, and get the blood pumping throughout your body.   It is also an opportunity for a little mental break, so you can refresh rest your eyes.

Know of others in your office who have terrible workspace ergonomics? Give Dr. Miller a call and she can give you a more personalized set up for your home/work desk.