Starting out you will need to look up and learn the following:
What is the name of each plant you come across? What does it produce?
What animals can use it for?
You need to build a base of knowledge of all these plants as they all play an important part in nature.
When you find an interesting plant that you do not know, look it up in your field book. If you have no field book with you, write a brief description and draw a simple picture of the plant in your notebook. Later at home or in school you can look in a nature book for the name of the plant. There are many good field books available at the library, bookstore or second hand book stores.
You will have to identify the more abundant plants in your area and what part they play in the ecosystem of the natural environment of where you are.
A good basis for study is to identify 35 plants that grow naturally in your environment, what is their purpose, and where do they grow.
Every plant has a purpose. Even those plants that we consider weeds provide food for bees, butterflies and sometimes the seeds are food for birds. Finding out why God put these plants on the earth can help us learn how to better take care of the world we live in.