Then look again at the two legged group. This time it might be something like those with bills and those without bills. This might separate all the birds from any others. Keep observing and sorting until all the toys have been sorted into their own groups. Check your work to see if any toy got placed in the wrong group.
Scientists sometimes write a key to how to classify things.
For example, there are keys to the wildflowers of different areas of the country. By looking at a plant carefully and answering a set of questions in a key, you can find out the name of a wildflower you find growing in a park. Has only two legs, go to 2. Has more than two legs, go to 10. Has a bill, is a bird, go to 3.