Choosing a well designed office chair is an essential step in achieving good computer ergonomics.

A good furniture will preserve and support the natural curves of your body back. In the neck and low back the spinal curves in, and in the middle back the spinal curves out.

To perform well the contour of the chair's back should match the curves of your back.

Sitting incorrectly with bad body position at a computer can be very much paining. Good ergonomics require a well designed office chair that properly supports the back, the proper monitor height, a low keyboard, and good shoulder placement to keep shoulders and forearms relaxed. These ergonomic recommendations can lead to hours of comfortable work.

First of all, try to avoid getting the pain in the first place - take regular breaks, make sure your seat is adjusted optimally, and so on. Basically all those things they told you to do on your orientation course. In case you don't work for a large multinational, and in the event you didn't have a fancy orientation day.

However, I presume you already have the pain and you want to get rid of it. I suggest yoga or pilates. There are some very simple yoga exercises you can do, which involve lying on your back and rotating your joints. I do them 3/4 times a week, sometimes for only 7/8 minutes, sometimes 20 minutes depending on my mood. The ones I did helped me with severe lower back and wrist pain. Take a look at this site for some ideas: I also recommend massage of any kind. I like Thai and Swedish.

• Get an exercise ball and roll around while you are at the computer. stretch your legs and hips and back, just take alittle break once in a while and stretch. Also you can adjust the height of your keyboard, that might make some difference. 
  
• Change your chair to those with 5 wheels and adjustable to the correct height. Lean backwards on the chair as you type. This will support your back and prevent it from slouching.
  
•  The first thing to do is to make sure your seating is at the right level, and you are not twisting,or bending your spine or neck while working. 
  
• Do a check on this, and likewise with the level of the screen.Is it just slightly below eye level,if not it may need adjusting. 
  
• This is the main cause of stress or injury to the neck and spine,in those who spend long hours at a computer. 
  
• There are ergodynamicly designed computer chairs available. Many companies have installed them to avoid,sick leave. Or staff having to go on leave due to a work related injury.
  
•  Inquire if this is an option were you are working. It actually saves the company money in the long term. 
  
• If you are self employed then look into the possible purchase of one of these chairs.
  
• They are approved and recommended by the American and Australian Health Authorities. I am not sure regarding other countries. It would obviously be claimable on your taxation. 
  
• Make sure you take a 5-10 minute break, standing away from your computer every 3hrs at least. 
  
• Take some of that time to do stretching exercises, for helping your neck and spine relax. 
  
• We tend to hold a lot of stress from inncorrect positioning in the trapezian muscles.Which are on each side at the base of the neck. The muscles will become quite taut if you put them under stress for long periods.
  
•  You can also do some shoulder and neck rolls and straighten and relax your spine a few times in between breaks.  If you think it is more than just inncorrect positioning/stress related.I would recommend you see a doctor or a chiropractor. Have them review your spine and neck for any other possible problems that this could be attributed to. 
• At home try a hot pack for stiffness and an ice pack for swelling.Try and sleep on a good mattress with only one pillow. that only fills the natural space between the shoulders and head.