Sometimes, if your remote control has been dropped or is quite old, you may need to replace it. Before you do troubleshoot it so you defiantly know to replace it. Here are some steps...
Step 1: Power
Firstly, replace the batteries. It seems obvious but it can help, although you may have replaced your batteries recently, a button may have been kept on by something squashing or pressing it. Batteries don't last long if the remote has to keep transmitting signals.
Step 2: Output
The remote may have full batteries but what if it is damaged internally? We'll luckily there is a clever trick, just get a camera, point it at the remote LED and hit some buttons, it should look like this ( the images compare what the LED looks like transmitting signals [look for a purple tint to the LED]) The first image shows a healthy remote and the second one shows a unworking remote. Also hit the key buttons that you use the most like power or the numbers.
Step 3: Move It
Try pointing it more directly at the TV's sensor it should look similar to the image... It's usually a small clear piece of plastic. Try getting the remote closer to it.
Step 4: Repair
If the items are valuable, take it too the local TV repair shop, the remote and the TV. As they contain warranty seals which could void your guaranty.
Step 5: Reciver
Alternately the actual recover (the device you want to operate) could be broken in that case follow step 4.