It is recommended that you get about 30 grams of fiber in your diet every day. Fiber is helpful for your body because it brushes out toxins from your digestive system.
I actually count how much fiber I get. Whenever I eat something that I suspect has a lot of fiber in it, I use my mobile phone camera to take a picture of it. When I am on my computer and I have free time, I look over the images I have taken with my mobile phone and estimate how much fiber I have consumed. The fiber content of food is usually available simply by reading the nutrition information on the package. For fruits and vegetables you can check out the website The Fiber Content of Common Foods.
If on a particular day you only get 15 grams of fiber, simply eat more fiber the next day. Be careful not to eat too much fiber as this can be bad for your digestive system. I estimate that more than about 50 grams per day is bad.
There are many different types of fibers, from soluble fiber to insoluble fiber. Some fiber comes from chicory root while others comes from wheat. I don't bother too much with the type of fiber I eat. I simply try to get a wide variety of different fiber from different sources.
If I am low on fiber for a particular day, there are some techniques I use to boost my fiber intake. One of these techniques is using Fibresure. Fibresure is pure inulin, a form os fiber. Some health experts say that inulin is not as good as other forms of fiber. Metamucil (the makers of Fibresure) claim that you can mix Fibresure with any food and it will not affect the taste. In practice what I find is that Fibersure tastes a little bit sweet (not necessarily a bad thing) and it has trouble mixing with certain beverages, especially Coke. One teaspoon of Fibresure contains 5.8 grams of fiber, so putting one tablespoon into a beverage will give you more than 16 grams of fiber, which is half a day's requirement.
Another fast source of fiber is the breakfast cereal Bran Plus from Uncle Tobys. Just one serve (about one cup) of this cereal has 20.4 grams of fiber in it, which is about two-thirds of your daily recommended intake. The problem with this cereal is that in my opinion it tastes really bad and dry. Whenever I eat Bran Plus (or any other similar bran cereal like All Bran) it makes me choke. I recommendation is to eat Bran Plus with a very large jug of water near you. Whenever you feel you cannot swallow the cereal, just chug down some water and you will be fine.