How do you keep your weight centered?

I realized today after a full day of snowboarding that my right leg felt completely fine but my left leg was super painfully sore (I'm goofy). This made me think about my riding and I realized that I think I've been keeping all of my weight on my back foot while riding. The whole time I was riding I was sure I was keeping my weight centered, but I guess I wasn't. I know that you're supposed to keep your weight even or maybe even have most of your weight on your front foot, but I guess I don't actually know how to do that. Does anyone have any advice for how to keep your weight centered?