The most accurate and detailed plant ID is accomplished with a flowering or fruiting structure present and plant specimen in hand. Become familiar with key features that are used in plant identification and terminology to help you describe plant morphology. There are numerous online native plant resources. Some of our go-tos are:
Illinois wildflowers
Minnesota wildflowers (has an advanced plant search)
Once you are familiar with common plant terms, botanical manuals and regional field guides are a perfect way to start identifying. We have many of our favorite ID guides listed HERE. There are also many Facebook groups dedicated to helping you ID your plant(s).