Seeds represent a wide range of things. Cereals, nuts, or legumes are all seeds. However, in the colloquial mindset, seeds are little things and we often add the word "seed" to the end of their name such as sesame "seed". I am using the term in that spirit. Seeds are among the highest fiber-containing foods. As a group they contain about 15% fiber. Some of them like chia/basil seed, flax/linseed or sesame have almost twice as much.
You can group seeds into two broad groups. Those that do not have a dominant flavor like pumpkin seeds and those that do like coriander seeds. Adding the former to foods such as salads, sprinkled on stews, potatoes or rice just adds the fiber, but does not change the taste, so you do not have to compromise. The latter group does change the taste (also roasting the former), so you have to feel comfortable with using them. Adding a small amount, however makes the dish more interesting and does not overwhelm your senses. Below are some of my favorite common seeds with increasing level of culinary challenge. Enjoy
1. Unroasted, very mild taste: pumpkin, sunflower, sesame, watermelon, hemp, poppy. When roasted they will have a stronger taste but still very mild
2. Slight taste but pleasant: nigella (onion seed), sumac (gives a subtle earthy sour taste)
3. Lots of taste. Start by adding a teaspoon full and then increasing it if you like it: coriander/cilantro, caraway, ajwan, cumin, mustard, fennel, dill, celery seed, nutmeg (ground), and fenugreek
4. Powerful taste. Start by adding a pinch and then increase it if you like it: chili seeds/flakes (dried chili is about 1/3 fiber), aniseed, black and white pepper, grains of paradise/guinea grains