Before you start scraping a particular website make sure you're not breaking any laws.
- If the website has an API for getting needed information use it!
- Do not harvest email addresses, personal phone numbers etc.
- Use a readable
User-Agentstring with your contacts (e.g. a website address).
- Make sure you do not create a significant load on the website. Make pauses between the requests.
- Read other articles and/or books about web scraping legal issues