If you tend toward C, you need to be very careful about taking fiber supplements. Some folks, like myself, can't tolerate them at all. Others can handle soluble fiber like Benefiber but not the psyllium husk fibers like Metamucil. Often, throwing bulk fibers into a stopped up colon can cause even bigger problems.
Water is the most important thing you can do for your digestive system. Above everything else, drinking lots and lots of water every day will help with C almost immediately.
I have found certain foods work quite well in "unplugging" a blocked system. Winter squashes like butternut and spaghetti, sweet potatoes and yams, barley and oat bran all seem to help get things moving.
When things get really out of hand, I will take Magnesium Citrate for relief. In terms of laxatives, I find this one to be the most effective and least unsettling for the bowel.