Siri was one of the revolutions from the new models of the iPhone that changed how smart phones were used. Now the way you interact with the device has shifted to a more task based use, instead of thinking about what you want to get done and then finding a function to perform it. Siri, like all built in apps and functions on the iPhone, has its own settings that allow you to alter how it works.
Go into the iPhone’s Settings and then go down to General, which is at the top of the third block of options above iCloud. In General select Siri, which is the second block of options. The first thing that you are going to have to determine is whether or not you want Siri on, and there is an On / Off switch at the very top of the available settings. If you choose to turn it off then there will be a pop up button to Disable Siri, which is not advantageous if you want to use it in conjunction with other iPhone functions. Directly below the explanation of the Siri switch will be a link to look at the Siri privacy rules, which are important since this is a voice command system and users could be concerned about saving information.
The next set of options is going to start with selecting language, which is important since you have to speak to Siri. If you are in the U.S. then it will be defaulted at English, but there are also other regional forms of English, French, Japanese, and German available.
Below that is an option for Voice Feedback, and the default is set to Always. You can also choose Handsfree Only, which will mean it only works in Handsfree mode. Next is a link to My Info, and when you select it you will be taken to the Contacts List to select your own Contact. This is not necessarily that important, but if you really want to integrate Siri into every part of your iPhone use then you may want to consider it. At the bottom there will be a Raise to Speak button that will be set to On as a default. This means that when you are using Siri you will hold the Home button and then raise up the iPhone, as if you were talking to a person through a call.