If your flowering plant is outside, there is no need for you to do anything to get your flowers to reproduce. Bees and birds will do the job for you. However, if you want your indoor plants to reproduce, use the hand pollination technique. This is a quick and easy process. Some plants have flowers with both the male and female part in the same flower. Other plants have separate male and female flowers. In either case you hand-pollinate the same way.
Search for the male parts of your plant's flower. These are the short stems in the middle of your flower called the stamen. Pollen is at the tip of the stamen.
Swipe a clean, dry cotton swab gently over the stamen to collect some pollen. Pollen is the male seed used to fertilize the female part.
Search for the longer stem in the middle of the flower. This is the female part of your flower and is called the pistil.
Rub the cotton swab with the pollen on it gently over the pistil. The pistil is sticky, so it will gather pollen into itself. The flower is fertilized.
Repeat these steps with as many flowers as you want. Use a clean cotton swab each time.