In Django, serializers are used to convert complex data types, such as Django model instances, into a format (e.g., JSON, XML) that can be easily rendered and transmitted over the network. Here are some popular methods commonly used in class-based serializers in Django:

1. `to_representation`: This method is used to customize how a serializer represents an object as a serialized output. You can override this method to provide custom serialization logic.

2. `to_internal_value`: This method is responsible for converting the deserialized data into internal values suitable for Django models. It allows you to customize the conversion process and perform any necessary data validations.

3. `create`: This method is used to create a new object based on the validated data. It is typically used in the serializer's `save()` method when creating a new instance.

4. `update`: This method is used to update an existing object based on the validated data. It is typically used in the serializer's `save()` method when updating an existing instance.

5. `validate_<field_name>`: These methods are used for field-specific validation. For example, if you have a field named `email`, you can define a method named `validate_email` to perform additional validation logic specific to that field.

6. `validate`: This method is used for general validation that involves multiple fields. It allows you to perform cross-field validation or apply validation logic that depends on multiple fields.

7. `get_<field_name>`: These methods allow you to customize how a specific field is retrieved or calculated. For example, if you have a field named `full_name`, you can define a method named `get_full_name` to return a formatted full name based on other fields in the serializer.

8. `get_<field_name>_display`: These methods are used to customize the display representation of a specific field. They are typically used for fields with choices, where you want to display the human-readable representation of the field's value.

These are some of the commonly used methods in class-based serializers in Django. By implementing and overriding these methods, you can customize the serialization, deserialization, validation, and behavior of your serializers according to your specific requirements.