Microsoft have released a guide in the form of an image which shows all of the Xbox One Kinect voice commands. The guide which was posted on Tumblr originally shows you all the voice commands, such as navigation, system commands , TV controls and more. In total there are 30 commands that you can use to control you're shiny new Xbox One, check out the image below:

Click to enlarge image:
pre_1385312676__xbox_one_voice_commands.


Here's some of the commands :

System Commands
Xbox on Wakes up Xbox One, turns on television and cable/satellite set-top box
Xbox turn off Puts Xbox One to sleep/off, can turn off television and cable/satellite set-top box
Xbox Shows menu of global voice command options and begins listening for the next command
Xbox select Shows voice command options for everything on the screen that are supported. Shows channel shortcuts during full screen TV viewing
Stop listening Stops Kinect from listening or cancels voice commands if Kinect is triggered during causal conversation
Xbox help Shows help menu with available options
Xbox use a code Triggers Kinect code scanning for QR codes
Xbox show notification Shows on-screen notifications
Identity
Xbox sign in/out or Xbox sign in as (person) Signs in/out an Xbox Live member
Gaming
Xbox record that Record the previous 30 seconds of gameplay
Xbox start a party Launches the Party app in Snap mode
Volume
Xbox volume up/down and Xbox mute/unmute controls volume of TV set
Navigation and Multitasking
Xbox go home or Xbox show my stuff Returns to Home screen
Xbox go to (activity) Launches specific games, TV shows, apps, notifications and sections of the dash.
Xbox show menu In full screen, shows menu for whatever is on the screen. At Home, shows menu for whatever is in the current window
Xbox go back Returns to previous screen or menu option
Xbox Snap (app) Launches activity in Snap mode
Xbox unsnap Unsnaps activity in Snap mode
Xbox switch Switches control of the activities in Snap mode and Fill mode
Communication
Xbox Skype (person) or Xbox call (person) Launches Skype call, must ba a person from your Skype favorites list on your Xbox One
Xbox answer/answer without video Answers incoming Skype call
Xbox hang up Ends Skye call
Xbox send a message Sends message to your Xbox Live friends
TV
Xbox watch TV Launches cable or satellite TV from set top box
Xbox watch (channel) Changes cable or satellite TV to specific channel when channel shortcuts are showing
Xbox show guide or Xbox OneGuide Launches OneGuide for cable or satellite TV subscribers
Media Controls
Xbox play/stop/pause/fast forward/rewind/faster/slower/skip forward/skip backward/next song/previous song Transport controls for media playback; play and pause also work for gameplay.
Xbox Play [music/video] Launches video and music playback
Bing and Internet Explorer
Browse to (website) Browse to the specific website when in Internet Explorer
Xbox Bing (name) Launches Bing and searches for the specific item/s

If you find that you're Xbox One isn't responding all that well you may need to do an audio calibration; this option can be accessed through the Settings menu.
Another tip is if you say : "Xbox select" you will see a list of available commands on screen.