the easiest way to increase fiber is to increase fruits and veges, and other non-processed foods. usually vegetarians who focus on eating healthy have no problems getting enough fiber. you should have 2-3 servings of fruit a day and as many veges as you can consume

for me that's about 2-4(maybe 5 if i'm lucky

) servings. If you eat most of these raw (some are better for you cooked!) you'll find they are more filling. Focus on the veges, fruit, beans, legumes, and grains. 1/4 cup of dry grain or legume is usually about 150 calories. that doubles in size when cooked! It's quite filling.
I'd also recommend adding coconut oil to your diet, and make sure you are supplimenting what you need to.
my breakfast consists of 1/3 - 1/2 cup dry oatmeal, added to microwaved water and allowed to sit and cook while cooling. and then add 2-3tsp honey - yum!
take fruit for snacks at work. a small salad with a favorite dressing makes a great snack as well, and serves to help wake you up. i have fun trying new veges and greens. some are disasters, others are fantastic!
A few of my favorite lunches:
1. quinoa and black lentils mixed with olive oil, salt and a variety of spices to taste plus 1-2 sliced soy dogs is yum! add 1-2 ears of fresh steamed corn.
2. bread made in breadmaker using whole wheat, spelt, amaranth seeds, and whatever else i feel like adding. slice thickly and on one side place an organic peanut butter, and on the other use raw almond butter (tastes like a rich walnut - yum!) add a salad with dressing or a favorite vege.
here's a general idea of what i did (and will get back to soon, with perhaps an increase of some things. I've had a stressful time and fell out of my patterns)
breakfast: 300-400 calories.
ride bike 5.5 miles as fast as I could, am i ever early?
snack on banana or small salad at work
10:00 starving! 150-300 calories or so from dried fruit/seedsnuts/salad/ or fruit.
12:00: lunches like the ones above: 500-700 calories usually.
sometimes mid afternoon snack, usually unhealthy like chocolate ~100-250calories
banana before i head out on ride home
ride home: 16 miles
arrive home, grab something proteiny, often a soy dog: 50-100 calories
dinner somewhere in the evening 300-500 calories.
simply by changing my diet to have as little processed foods (ok, so there was soy dogs and chocolate

), i didn't notice the change in my body until i realized i had to go and purchase bike shorts in size small - I wasn't trying to change my body! i lost no weight, but then it's not about numbers. though bike shorts are too expensive to have to buy a whole new collection

never thought I'd be a little frustrated with weight loss! lol