Begin by ensuring that both your MongoDB and Weaviate instances are properly set up and running. For MongoDB, this means having access to the database with the necessary credentials. For Weaviate, make sure it is deployed and accessible, with the schema designed to accommodate the data you plan to migrate.

Use MongoDB’s native tools to export data. The `mongoexport` utility can be used to export data to a JSON or CSV file. For example, use a command like:
```
mongoexport --db yourDatabase --collection yourCollection --out data.json
```
This command exports the specified collection to a JSON file called `data.json`.

After exporting, review the JSON structure to ensure it aligns with Weaviate's requirements. Weaviate uses a certain schema, so you might need to transform your data to match the schema, such as adjusting field names or data types. You can use a script, written in Python or another language, to parse and transform the JSON data.

Before importing data, define a Weaviate schema that reflects the structure of your data. This involves specifying classes, properties, and data types. Use Weaviate's RESTful API to create the schema. An example API call in JSON format might look like:
```json
{
"class": "YourClass",
"properties": [
{
"name": "propertyName",
"dataType": ["string"]
}
]
}
```
Use a tool like `curl` to send the schema to Weaviate.

Develop a script to read the transformed JSON data and insert it into Weaviate. You can use Python with `requests` library to interact with Weaviate’s REST API. The script should iterate over the JSON records and use the API to create objects in Weaviate, like:
```python
import json
import requests

with open('transformed_data.json', 'r') as file:
data = json.load(file)
for record in data:
response = requests.post(
'http://your-weaviate-instance/objects',
json={
"class": "YourClass",
"properties": record
}
)
print(response.status_code, response.json())
```

Execute the script to start importing data into Weaviate. Ensure that the script handles any potential errors, such as network issues or data validation errors. Monitor the output to verify that the data is being successfully inserted.

After the import process, verify that the data in Weaviate matches the original data in MongoDB. You can perform sample queries using Weaviate’s API to ensure that the data is correctly stored and accessible. Check for any discrepancies and resolve them by re-importing or adjusting the data as needed.

By following these steps, you can successfully migrate data from MongoDB to Weaviate without relying on third-party connectors or integrations.