Can I track my iphone if someone steals it and turns it off + takes the sim card out? And can they do something to prevent me from tracking my phone?
Can I track my Iphone 5 if it is stolen and turned off?
You need to have set up Find My iPhone/iPad on your device prior to it getting lost or stolen. If you did, go to https://www.icloud.com/ in your web browser. When you log in, Find My iPhone/iPad will immediately begin trying to locate your device.
However, find my iphone will not work if the device is offline or has been reset to factory settings.
I suggest all the idevice users install some free app like ilostfinder on our devices. It will take pics of the thief or finders when she/he tries to open your device and then send the pics to your email. You may get it back or at least prevent the thief next time with the app.