How to start code refactoring?

He beginning, the easiest way to start with refactoring is to do it on a method level.
A quick thing to check first is if the method is too long.
An extended method is a classic sign of the process being too much, and it would probably benefit by splitting it into several other smaller*methods .

METHODS OF REFACTORING

Get rid of switch statements.
Make your conditionals descriptive.
Use guard clauses to avoid nested if statements.
Avoid code duplication.
Functions should only do one thing.

The best way to start refactoring code is to use a process such as the "Red-Green-Refactor" cycle. This process basically involves making small changes, testing the code to make sure it still works as expected, and then making further improvements. This process helps ensure that the code is not harmed during refactoring.

It is also important to do an analysis of the code before refactoring. This analysis can help identify areas of the code that can be improved and provide insight into the types of changes that should be made. This can help reduce the risk of introducing bugs or issues while refactoring.