Begin by ensuring you have access to AWS with the necessary permissions to read from the S3 bucket. You’ll need AWS credentials (Access Key ID and Secret Access Key) configured on your machine. Use the AWS Management Console to create an IAM user with `AmazonS3ReadOnlyAccess` policy and download the credentials.

Set up a RabbitMQ server if you haven’t already. You can do this on-premises or using a cloud-based solution. Ensure that your application has access to the RabbitMQ server and you have the connection details (hostname, port, username, and password).

Install the AWS SDK for S3 and a RabbitMQ client library for your programming language of choice. For instance, if using Python, you can use `boto3` for AWS and `pika` for RabbitMQ. Install these libraries using a package manager like `pip` with the following commands:
```
pip install boto3
pip install pika
```

Develop a script that connects to your S3 bucket and downloads the data you wish to transfer. Use the AWS SDK to list and fetch objects from the bucket. Here’s a basic example in Python:
```python
import boto3

s3_client = boto3.client('s3', aws_access_key_id='YOUR_ACCESS_KEY', aws_secret_access_key='YOUR_SECRET_KEY')
bucket_name = 'your-bucket-name'
object_key = 'your-object-key'

response = s3_client.get_object(Bucket=bucket_name, Key=object_key)
file_content = response['Body'].read().decode('utf-8')
```

Write a function that connects to your RabbitMQ server using the RabbitMQ client library. For instance, in Python with `pika`:
```python
import pika

connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channel = connection.channel()
channel.queue_declare(queue='your-queue-name')
```

Extend your script to publish the data downloaded from S3 to the RabbitMQ queue. Ensure that the data is appropriately formatted (e.g., JSON, CSV) before sending:
```python
channel.basic_publish(exchange='', routing_key='your-queue-name', body=file_content)
print("Data sent to RabbitMQ")
```

Finally, test your setup by running the script to ensure data is correctly transferred from S3 to RabbitMQ. Monitor the RabbitMQ queue to verify the messages are being received. You can use RabbitMQ Management Plugin for monitoring. Adjust logging and error handling in your script for better reliability and troubleshooting.

By following these steps, you can effectively move data from S3 to RabbitMQ without relying on third-party connectors or integrations.