Instructions
Try This First
Make sure the Wii Sensor Bar is plugged into the back of the system. If it isn't, or if it's loosely connected, your Wii Remote will not be able to communicate with your console.
Verify that your Wii Remote's batteries are fresh. Replacing the batteries can fix many problems with the remote acting erratically.
Ensure that other items in the room aren't interfering with the Wii. Infrared sources such as candles and stoves can confuse the Wii Remote, as can radio frequencies from other wireless devices close by.
Nearly Foolproof Method
Turn off the Wii Console. Unplug the power cord from the wall. After a few seconds, plug it back in.
Power the Wii back on, and wait until the Health and Safety notice appears onscreen. Open the small latch on the front of the Wii and locate the "Sync" button. Hold it down for 15 seconds. Now all of your Wii Remotes will be reset.
Remove the battery cover from the Wii Remote you wish to use. Press the red button you find there, and notice that the blue light on the front of the Wii is blinking.
Press and release the "Sync" button on the front of the Wii console once again.
Notice the blue light on the Wii Remote. Once it is lit, the controller has been synced. It should now behave properly.