Which controller are you using: Xbox etc?
press the signal button on the top of the controller and also press the signal button on the xbox next to the memory card port, it has a logo that looks like ))) next to the button. that should reset both the controller and the xbox to sync up to each other.
You might have to do that a couple of times to get it to work. sometimes the first time you do it, doesn't work.
Also another thing is to change batteries if they are old are sometimes if the batteries come with the box then change them anyway because sometimes they do not work.
Let me know if that works. Sync first, then try new batteries and see if that works, if new batteries doesn't work then try the sync again with the new batteries.
Another thing is unplugging the controller then plugging it back in. try that with the xbox off and then plug it in before you turn xbox back on and then try it the other way. xbox on, unplug controller, then plug back in.
Most of the time it just needs to sync from xbox 360 to controller.
Here is a link that you can find the buttons I am talking about to sync your controller with your xbox 360: https://support.xbox.com/en-US/xbox-360/accessories/connecting-game-controllers.
Another link here to sync: http://www.wikihow.com/Connect-a-Wireless-Xbox-360-Controller.
Keep me posted and let me know if it works.
Also how old is the xbox 360 and the controller? Did you try a different controller (maybe that controller is defective)?