Make sure you have the entire flower or stalk in your photo.
After taking the photo, you might consider cropping it to eliminate distracting elements and to concentrate the viewer’s attention on the iris depicted.
Be conscious of focus – make sure your photo has the flower and/or stalk in focus.
Be conscious of lighting – diffuse light (such as on cloudy days) usually produces a better photo than harsh light such as midday sun.
As much as possible, try to eliminate distracting background elements from your photos. This can be difficult if the iris is in the ground, but if it is in a pot, it might be possible to get a less cluttered shot by moving the pot elsewhere. Some people use a background screen to block out unwanted background elements. It is also the entrant’s choice whether to reduce distracting elements by cutting the stalk and displaying it in a vase in a more controlled environment.
Neatness counts! Make sure your iris plant is free of weeds, debris, or insect leavings.
Hope this is helpful. Above all, have fun!