A bag is useful for collecting large leaves. You could try to find out what trees they are from
Use a magnifying glass to look closely at what you find. Can you see the smaller parts like the parts which make up the flower?
Collect fallen leaves, twigs, seeds and petals in a pot or jar. Remember not to pick wildflowers or plants
Record what you find and make sketches in a notebook
A guide book will help you identify the plants you find. You can borrow one from the library.