How To Identify Whether There Is Life On Other Planets?

How Can We Identify Whether 

There Is Life On Other Planets

So to find life on other planets, the following things should be available:

1.Its temperature and gravity.

2.Its rocky surface.

3.The presence of the atmosphere

4.The presence of water and oxygen.

5.The presence of other greenhouse gases, including carbon dioxide, which keeps the planet warm

6. The Moon, which holds the spinning of planets in its position. 

7. A protective layer like the ozone layer that protects from harmful radiation.