Ensure that your Excel file is well-organized. Each column should have a clear header that represents the data it holds. Make sure there are no empty rows or columns, and the data types are consistent (e.g., numbers, text, dates).

Open your Excel file and navigate to 'File' > 'Save As'. Choose 'CSV (Comma delimited) (.csv)' as the file type and save your file. This converts your Excel data into a CSV format that can be easily read and processed by scripts.

Go to the Google Cloud Console (https://console.cloud.google.com/) and create a new project or select an existing project. Enable the Firestore API by navigating to 'APIs & Services' > 'Library', then search for 'Firestore' and click 'Enable'.

Download and install the Google Cloud SDK from https://cloud.google.com/sdk/docs/install. Follow the instructions for your operating system to set it up. Authenticate with your Google account by running `gcloud auth login` and set your project using `gcloud config set project [YOUR_PROJECT_ID]`.

Write a Python script to read the CSV file using the built-in `csv` module. Use `csv.reader()` to parse the file and store the data in a list of dictionaries, with each dictionary representing a row in your CSV.

```python
import csv

data = []
with open('your_data.csv', mode='r') as file:
reader = csv.DictReader(file)
for row in reader:
data.append(row)
```

Install the Firestore client library using pip: `pip install google-cloud-firestore`. Then, in your Python script, set up the Firestore client:

```python
from google.cloud import firestore

db = firestore.Client()
```

Make sure you have your Google credentials set up. You can do this by setting the `GOOGLE_APPLICATION_CREDENTIALS` environment variable to the path of your service account key JSON file.

Use a loop in your Python script to iterate over the list of dictionaries (from step 5) and upload each row to a Firestore collection. Choose a suitable collection name and document ID strategy (e.g., use a unique field from the data or Firestore's auto-generated IDs).

```python
collection_name = 'your_collection_name'

for row in data:
# Use Auto-ID
doc_ref = db.collection(collection_name).document()
# Or use a specific field as ID
# doc_ref = db.collection(collection_name).document(row['unique_field'])
doc_ref.set(row)
```

Run your script to transfer the data from the CSV to Google Firestore. Check the Firestore console to verify that the data has been uploaded correctly.