If you write XPath it is helpful to have a quick way to test what you are doing. You can give it a try using an online tool XPathTestBed. This is pretty easy to use.
If you are doing XPath on page source you can use the Console built into Chrome or Firefox and get immediate results. Just F12 to get into the developer tools. Go to the Console, and enter the following to get all div tags for example.
Very useful and easy to use.