In a descriptive essay you can describe:

• A summer evening
• a night at a friend’s house
• delicious Thanksgiving turkey

Basically you are free to describe anything you want. Just do it well.
You will hardly need doing any research or (though sometimes it may be necessary) to write a descriptive essay. You write about something from your point of you. Since descriptive essay is mostly a sensory piece of writing, mention how the object looks, smells, sounds, tastes, what emotions it evokes. You can present your description as a complete list of details. Other alternative is to tell the reader an absorbing story keeping him involved and intrigued in the course of the whole narrative. In a descriptive essay metaphors and images prevail over statistics and facts.

Mind these 3 rules while preparing your essay:

• Combine actual and abstract ideas.
• Avoid using too many metaphors and adjectives.
• Describe by showing, not merely stating. You show something through a variety of carefully selected examples.

If you manage to draw an image of something in language that means you can write a good descriptive essay.