Begin by logging into your Omnisend account. Navigate to the section where you can export your data, typically found under reports or contacts. Choose the data you want to export, such as contacts, campaigns, or reports. Select the format for export, preferably CSV or JSON, as these formats are easily manageable and supported for import into DuckDB. Download the exported file to your local machine.

Open the exported file in a spreadsheet application (like Excel) or a text editor to inspect the data. Ensure that the data is well-structured with consistent delimiters and no formatting errors. Clean any unnecessary headers, footers, or malformed entries. Save the cleaned file, ensuring it remains in a CSV or JSON format.

If you haven't already installed DuckDB, download it from the official website and follow the installation instructions for your operating system. DuckDB is lightweight and can be set up quickly on most environments.

Open your command line interface or terminal and start DuckDB by executing the `duckdb` command. Create a new database file using SQL commands within the DuckDB shell. For example, you can use:
```sql
CREATE DATABASE omnisend_data.duckdb;
```
This command will create a new database file named `omnisend_data.duckdb` in your working directory.

Define the schema for your table in DuckDB that matches the structure of your imported data. Use the `CREATE TABLE` SQL command to set up the table with appropriate columns and data types. For example:
```sql
CREATE TABLE contacts (
id INTEGER,
email VARCHAR,
name VARCHAR,
signup_date DATE
);
```

Use DuckDB's built-in SQL commands to load data from your CSV or JSON file into the newly created table. For a CSV file, you can use:
```sql
COPY contacts FROM 'path/to/your/exported_file.csv' (DELIMITER ',', HEADER TRUE);
```
For a JSON file, you can use:
```sql
COPY contacts FROM 'path/to/your/exported_file.json' FORMAT JSON;
```
Ensure you provide the correct path to your data file.

After loading the data, it’s crucial to verify that the import was successful. Run a simple SQL query to check the data in your DuckDB table, such as:
```sql
SELECT * FROM contacts LIMIT 10;
```
This will display the first ten rows of your table, allowing you to confirm that the data appears as expected. Check for consistency, correct formatting, and completeness.

By following these steps, you can move data from Omnisend to DuckDB without relying on third-party tools or integrations.