Make a drawing of a forest. Include plants that are found together. Show dominant, canopy trees, such as oaks or pines. Also show understory trees, which live "under" the canopy. Then show plants that live on the forest floor, such as ferns or mosses. Lastly, don't forget parasitic vines, which climb up taller plants. Remember: There are more shrubs and shorter plants at the edge of a forest, where they get more light. They also tend to be "thicker," or closer together, there. Also, where there is one plant, there are usually more of the same species. For instance, a forest dominated by Black Oak and White Oak will have many of those two species, and if one tree has Poison Ivy crawling up it, then others probably do too.
You can find out which plants live together, by looking at the "Associations with Other Plants" box near the bottom of each Species Page.
To make your forest more realistic, you could add some fallen trees and stumps. For an extra challenge, include some animals and fungi.
Clearly label all organisms in your drawing.