diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index b92bd2a1..c5ec2bad 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -21,14 +21,16 @@ This project is in its early stage — so **you’re welcome to help build it fr
    ```bash
    git checkout -b my-feature
    ```
-4. **Start coding!** Edit files, add features, fix bugs.
-5. **Commit and push**
+4. **Set up your development environment** (see [README.md](README.md#-getting-started-development))
+5. **Start coding!** Edit files, add features, fix bugs.
+6. **Test your changes** (see section below)
+7. **Commit and push**
 
    ```bash
    git commit -m "Add: my feature"
    git push origin my-feature
    ```
-6. **Open a Pull Request** on the main repository. Your PR must target the `master` branch!
+8. **Open a Pull Request** on the main repository. Your PR must target the `master` branch!
 
 ---
 
@@ -48,6 +50,58 @@ We’ll also add `good first issue` and `help wanted` labels as the project evol
 
 ---
 
+### 🧪 Testing Your Changes
+
+Before submitting a pull request, make sure to test your changes locally:
+
+#### 1. Frontend Testing
+
+**Run the development server:**
+```bash
+npm run dev
+```
+- Manually test your feature in the browser at `http://localhost:5173`
+- Check that your changes work across different screen sizes (responsive design)
+- Open DevTools (F12) and check for console errors or warnings
+
+**Run linting and formatting checks:**
+```bash
+npm run lint        # Check code quality
+npm run lint:fix    # Automatically fix issues
+npm run format:check # Check if files are formatted correctly
+npm run format      # Format all files
+```
+
+**Build for production (optional but recommended):**
+```bash
+npm run build
+npm run preview     # Preview the production build
+```
+
+#### 2. Backend Testing
+
+**Make sure the backend is running:**
+```bash
+cd backup_existing_project/backend
+source venv/bin/activate  # or venv\Scripts\activate on Windows
+python3 run.py
+```
+
+**Test your API changes:**
+- Use tools like [Postman](https://www.postman.com/) or [curl](https://curl.se/) to test API endpoints
+- Check that error handling works correctly
+- Test with invalid inputs to ensure proper validation
+
+#### 3. Before Committing
+
+- Ensure no console errors in browser DevTools
+- Ensure linting passes (`npm run lint` shows no errors)
+- Ensure formatting is correct (`npm run format:check` passes)
+- Test on both desktop and mobile browsers if possible
+- Write clear, descriptive commit messages
+
+---
+
 ### 📚 Guidelines
 
 * Keep code clean and readable
diff --git a/README.md b/README.md
index 649db043..88034610 100644
--- a/README.md
+++ b/README.md
@@ -78,9 +78,16 @@ notesvault/
 
 ### Prerequisites
 
-- **Node.js 20+** (for frontend)
-- **Python 3.x** (for backend)
-- **npm 10+**
+- **Node.js 20+** (for frontend) - [Download](https://nodejs.org/)
+- **Python 3.8+** (for backend) - [Download](https://www.python.org/)
+- **npm 10+** (usually comes with Node.js)
+
+#### Verify installations:
+```bash
+node --version
+npm --version
+python3 --version
+```
 
 ### 1. Clone the repository
 
@@ -100,11 +107,19 @@ The frontend will run at `http://localhost:5173`
 
 ### 3. Set up Backend (Flask)
 
-**Terminal 2:**
+**Terminal 2 (new terminal window):**
+
+First, set up Python virtual environment:
 ```bash
 cd backup_existing_project/backend
+python3 -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+Then install dependencies and run:
+```bash
 pip install -r requirements.txt
-python run.py
+python3 run.py
 ```
 
 The backend API will run at `http://localhost:5000`
@@ -116,6 +131,32 @@ The backend API will run at `http://localhost:5000`
 
 The frontend is configured to proxy API requests to the backend automatically.
 
+### Troubleshooting
+
+**Backend won't start - "Port 5000 in use"**
+```bash
+# Check what's using port 5000
+lsof -i :5000
+
+# Kill the process (replace PID)
+kill -9 <PID>
+
+# Or start on a different port
+python3 run.py --port 5001
+```
+
+**Command not found: python or pip**
+- Use `python3` and `pip3` instead
+- Verify Python 3 is installed: `python3 --version`
+
+**npm install fails**
+- Clear npm cache: `npm cache clean --force`
+- Delete `node_modules` and `package-lock.json`, then try again
+
+**Module not found errors on backend**
+- Ensure virtual environment is activated (should see `(venv)` in terminal)
+- Reinstall requirements: `pip install -r requirements.txt --force-reinstall`
+
 ---
 
 ## 📜 Available Scripts