Magento: Setup Cron Jobs In Custom Module

Sometimes in magento we need some task to be run , i.e. these tasks/actions need to be performed periodically like:………….  

- Refreshing Catalog Price Rules
- Sending Newsletters to customers
- Generating Google Sitemaps and submitting it to Google
- Sending Customer Notification about product price change or product back in stock
- Updating currency rates
- Making backups
- Cleaning logs