According to the American Heart Association, the average American takes in 15 grams of fiber. Several organizations recommend 25 - 30 grams a day. The American Dietetic association recommends 25 - 35 grams a day.
If your intake is 15 grams or less and you want to increase your fiber intake, increase it gradually. If you jump from 15 to 35 grams a day, it may cause stomach cramping and gas. Make sure you also increase your water intake when you start increasing your fiber intake. This will also reduce any cramps you get.