I make a conscious mental check of my muscles periodically when sitting at the computer or at a table discussion. As a child when I was even shorter than I am now, I sat with only the balls of my feet touching the floor because I couldn't reach the floor from my chair. This evolved into a habit. I must remind myself to keep my feet flat on the floor and to relax my shoulders as well. Periodic stretches at my desk help relieve this tension as well.
A therapeutic massage every two weeks would also help my muscles relax and remove the knots that build up from the tensions of daily life.