What is the best steps to apply preventive maintenance in the plant?

The main steps to apply preventive maintenance are:

1- Define the components of the system which needs to be maintained periodically regarding the system condition. 

2- Define the periods of maintenance for the components depending on the operation conditions, the components' materials conditions.

3- Include the designer's input for the maintenance within manuals and catalogs of the system.

4- Prepare a schedule for maintenance that includes all the maintenance periodic events.

5- Prepare your spare parts required for maintenance implementation.

6- Record all actual maintenance jobs.

7- Analyze and compare between the actual and planned in order to evaluate and update the periodicity of the jobs.

Side note: You can use preventive maintenance programs. These program can help you in keeping the records and reminding of the jobs required.

Best Regards