Although there really isn't a first step because this is a cycle, we can start with evaporation, which is often the most well known stage. Evaporation happens when the sun heats the water, and the water turns into water vapor. When the water molecule goes from liquid to gas in this process, it rises up into the atmosphere.

Next comes condensation. This is the stage where water molecules in the atmosphere condense to form clouds. After that when it's time for precipitation, the water comes back down to the ground of the earth. It can come down in many forms; some of them include rain, sleet, or snow. 

Then, the water molecule may go through either runoff or infiltration. What step the water molecule goes through next mostly depends on where it lands on the Earth. If it lands on the soil, it would go through infiltration, which is when the molecule seeps into an underground aquifer. However, it may also collect in bodies of water, such as a lake or the ocean, or even in puddles and go through runoff.

After a water molecule goes through runoff, it would then go through evaporation, and it would be back to where we started. However, after a water molecule goes through infiltration, it would be sucked in by a plant's roots from the soil. Then, the plant would use the water molecule to perform photosynthesis. During photosynthesis, the plant would often release water vapor, and it would rise back up to the atmosphere. This step is called transpiration. It is a parallel step to evaporation, as they would both lead back to condensation next (which I explained earlier).

According to the Law of Conservation of Matter, the water molecules around you have existed for millions of years, and will continue to exist for millions of years. It is astonishing to think about how long a water molecule would have gone through this cycle, and the journey that led up to it.

*All sources come from my Biology notes!