Begin by ensuring that your Excel data is clean and well-structured. Remove any unnecessary formatting, empty rows, or columns. Save your Excel file in a CSV format, as CSV is a simple and widely accepted format for importing data into databases.

Open your Teradata SQL Assistant or any Teradata client tool that allows you to execute SQL queries. Ensure you have the necessary login credentials and permissions to access the Teradata database where you intend to load the data.

Define the schema of the table in Teradata where you will load the data. Use the CREATE TABLE SQL statement to establish a table with columns matching the data types of your CSV file. For example:
```sql
CREATE TABLE target_table_name (
column1_name DATA_TYPE,
column2_name DATA_TYPE,
...
);
```

Use a secure method to transfer the CSV file from your local machine to the Teradata server. This can be done using tools like SFTP or SCP. Place the CSV file in a directory on the server that is accessible by Teradata.

Use Teradata's native tools such as the Teradata FastLoad or the `LOAD DATA` SQL command to import the CSV data into the target table. Here's an example using the `FastLoad` script:
```plaintext
LOGON your_teradata_server/username,password;

DATABASE your_database_name;

BEGIN LOADING target_table_name
ERRORFILES error_1, error_2;

DEFINE
column1 VARCHAR(255),
column2 INTEGER,
...
FILE= 'path/to/your/file.csv';

INSERT INTO target_table_name
VALUES
(:column1, :column2, ...);

END LOADING;

LOGOFF;
```

Once the data is loaded, run a SELECT query in Teradata to verify that the data has been accurately transferred. Check for discrepancies between the original CSV file and the target table to ensure data integrity.

After successful data transfer, remove any temporary files from the Teradata server to maintain a clean environment. Document the steps and any scripts used in the process for future reference or to facilitate repeated data loads.

This guide outlines a methodical approach for transferring data from an Excel file to Teradata Vantage without relying on third-party tools, focusing on using native Teradata utilities and SQL commands.