How to properly send curl post data with headers and parameters? or What's the best way to format cur

Random thought: are you sure the server’s not redirecting? Add `-L` to follow redirects. Also, some APIs need `Accept: application/json` header too.

For auth, here’s a clean example:
```bash
curl -X POST https://example.com/api -H "Content-Type: application/json" -H "Authorization: Basic $(echo -n 'user:pass' | base64)" -d '{"key":"value"}'
```