Get rid of crappy chairs and replace with comfortable Aeron chairs
Attractive girl sitting on an office chair
Top 11 Best Ergonomic Office Chairs My picks are the Serta, Viva and Walker ones.
Herman Miller Aeron chair- you can't mention task chairs without mentioning the Aeron, every task chair made in the last 25 years is a descendant of this chair.
Using proper posture is an important part of staying out of back pain and neck pain. Check out this article for some great tips to maintain good posture in any situation.
Gravity balans Chair by-Peter Opsvik. "The only recliner to offer zero gravity positions from active sitting to relax." From Varier Furniture.