All types of plants, from fruits and vegetables to flowers and trees, produce seeds to procreate. While certain plants reproduce through other means, such as rhizomes, seeds are a surefire way to grow a new plant, as long as they are pollinated. If you want to find seeds in plants, it is usually pretty easy to do. If that plant produces flowers or fruit ,then finding the seeds in the plant will be easy because you know where they will develop.
Flowers
Wait for the flowers to die.
Allow the flower to dry on the plant. They will form capsules or seed pods.
Pick the capsules or seed pods off of the plant. These will be full of seeds for that kind of flower.
Fruit and Vegetables
Wait for the flowers to turn into fruit.
Pick tomatoes, peppers and melons when they are ripe. Pick squash, eggplant, beans and peas when they are dry and hard.
Open the fruit. The seeds will be inside.
Trees
Wait for the trees to flower. Some trees produce seedpods that are quite noticeable, while conifers produce cones that contain seeds.
Wait for the seedpods or cones to dry on the tree.
Pick the seedpods or cones off of the tree and open them. Seeds will be inside. Shake the pine cone to loosen the seeds inside of it. They should fall out if it is dry enough.