Define your purpose. As pointed out by Elder and Finch, through history and into the modern day, nature writing has fulfilled myriad purposes: advocacy for environmental protection and social justice, commentary on human behavior and connecting scientific ideas to personal experiences, among others.
Immerse yourself in the surroundings you want to write about and observe. As Ron Harton of the website Nature Writing for Readers and Writers states, "Nature writing begins with observation." Use all of your senses to observe deep and minute details that wouldn't be obvious to the average passerby. You may want to take photographs, make sketches or write down your observations in a journal.
Connect your observations to your purpose. For example, if you are inspiring people to preserve a rare tree in your area, what details from your observations encourage that purpose? If you want to describe the joy you feel when walking your favorite trail, what experiences have you had that show that?
Conduct research where needed to fill in the blanks. Elder and Finch describe how nature essays often build on scientific knowledge while adding a personal dimension that is often missing during pure scientific inquiry. For example, your observations may be bolstered by research conducted by zoologists and botanists about the animal and plant species common in your area. Researching geological history may help you to express the timelessness of a particular location or describe land formations.
Outline your essay. Some writers benefit from detailed outlines of their progress, while others might need only a few jotted notes about what should be included in what section. Include an introduction that pulls your reader onto the trail or into the forest with you, and don't forget a conclusion to wrap up any loose ends.
Write your essay. Concentrate on evoking strong images that will help your readers to see and experience what you have seen or experienced that helps to illuminate your purpose in writing the essay. Be selective to keep the essay moving and choose the images that are strongest or most relevant to your purpose.
Reread and revise your essay. Ask yourself how closely you kept to your purpose and whether your writing expresses what you wanted it to express. Having a friend or peer read your essay and provide feedback will give you more information on how readers will respond to your writing.