Many times a faucet may stop working as well as it used to. This may be due to the number of minerals and hardness of your water. Some people that use well water may find that scale will build up over time, making the spray nozzles clog and lose effectiveness.
In these cases, a baggie with some vinegar might do the trick. Let it soak for a bit, and you should be good to go. For more severe problems then you may have to use a more effective chemical, such as a robust bathroom cleaning solution. Be careful here, though – the acids in these can be hazardous to your health.
For cleaning the body of the faucet, a little household cleaner may be all you need to bring the finish back to looking new.