I always emphasize the importance of fiber in one's diet.  Fiber is found in plant foods, and is classified as a carbohydrate, but it is not absorbed as calories. Fiberous foods can even affect the absorption of other nutrients. Fiber is important because it helps to keep one full by slowing down the absorption of foods and absorbing water. Fiber that is actually "fibrous" in texture, such as cauliflower, broccoli, nuts, and seeds will clean out the intestinal tract by "scraping" the inner membranes and potentially removing cancerous or carcinogenic cells. We need a balance of soluble and insoluble fiber in our diets for optimal health.

       Soluble fiber forms a gel like substance in water, which helps one to stay full and therefore can aid in weight loss. It can also help with reduction of IBS symptoms and lose stools, control sugar levels and prevent ulcers. Soluble fibers ferment in the colon and act as a prebiotic.  It is typically found in the fleshy part of fruit like the pectin in apples, pears, and plums. It is also found in almonds and other nuts, oatmeal, flaxseeds, beans and legumes, and root vegetables like sweet potatoes.
       Insoluble fiber is found in the skins of potatoes and fruits and vegetables (like apple/pear skin), and cauliflour, green beans, zucchini, and celery. These are the stalky/woody indigestible parts of the plant which causes bulking of the stool. As usual, the best way to get what you need in terms of nutrition and fiber is to eat a diet high in a variety of plant foods, like vegetables and legumes along with some seedy fruits or fruits with a skin. 
       Dietary fiber binds to cholesterol in the blood, and helps to "recycle" it. If you have high cholesterol, the first defense should be to increase your daily level of fiber intake. It also improves your glucose tolerance. If you are serious about improving your health, be sure to consider your fiber sources. Be wearying of consuming snack foods that mask themselves as healthy choices. An example would be a fiber muffin from Tim Hortons or McDonalds (around 350 kcal, 15g fat, and 54 total carbs). Just because they are made with bran does not mean that they are a healthful choice. Making homemade bran muffins with clean ingredients (ie apple sauce instead of margarine, whole wheat flour instead of refind four, and skipping the processed sugar) would be a smart snack choice. Rather than grabbing a costly fiber snack bar (that contains sugar, palm kernel oil, fructose and glycerin) have a handful of nuts with a some vegetable sticks or grapes.
You can find detailed information about the fiber content in almost all foods at this great site.

    
 Here are some of my recommended ways to get your fibre.

1. Quest Protein Bars 170 kcal, 20g protein, 5g fat, 17g fibre (24 total carbs)

2. Artichoke (100g) 47kcal, 33 g protein, 5 g fiber (11 g carbs)

3.Fibre One Honey Clusters 1 cup 160kcal, 3 g protein, 13 g fibre, 1.5 g fat, (44g total carbs)

4. Oat bran, 1 cup cooked 88 kcal, 7g protein, 6g fibre, 2g fat (25g total carbs)

5. Wheat bran, 1 cup raw, 125 kcal, 9g protein, 25g fibre, 2g fat, (37g total carbs)

6. Chickpeas 1 cup 286 kcal 12g protein, 11g fibre, 3g fat (54g total carbs)

8. Broccoli 1/2 cup cooked 27kcal, 2g protein, 3g fibre, 0g fat, (6g total carbs)

Remember to drink a lot of water when increasing your fibre intake to prevent upset stomach and constipation! Eating a high fiber diet can lead to improved gut health, but may leave you a bit gassy and bloated. Add small amounts of fiber and increase over a couple weeks. If you have IBS add one food item at at time to determine what types of fiber will work for you. I personally love cauliflower (am having some braised in apple cider with a touch of maple bacon cooked on top for flavour for dinner) and cabbage, but can only eat VERY small amounts of these foods raw. Fiber is just another reason why eating whole foods is so important--uou will not find much fiber in fast food or frozen dinners!