A majority of flowering plants including annuals, perennials, vegetables, trees and shrubs carry both the male and female components of the plant on the same flower. There are some plants, however, that either grow into individual male or female plants or produce individual male or female flowers on one plant. To tell the difference between male and female flowers you'll need to compare how each one looks to spot their differences.
Look over the flowers of your plant to find two that don't resemble one another structurally inside of the flower. Two different flowers may be found on the same plant, or you may need to look for two individual plants to find two difference ones.
Examine the inside of the two flowers. One flower will have a single tube with an enlarge cap on the end, called a pistil. This is the female flower, as the pistil leads to the ovary of the plant. Often behind the flower head an immature fruit or pod of the plant can be seen.
Check the inside of the other flower. This flower should hold approximately five or more short stalks with what resembles a pompom on the end. Each stalk is called a stamen. Pollen is produced on the puffy end of the stalk, called the anther. Seeing multiple stamen signals this is the male flower.
Compare the male and female flowers to note other differences among the plants for your own reference. These can include variations in the vibrancy in color, placement of the flower along the plant, which may be close to the main stem or farther out, and the size of the flowers.