Locate a thin piece of paper. Then, take a look at your bridge. Try to insert the paper underneath the bridge, even if it's only the corner. Ideally, you won’t be able to. However, if you can, it means that your bridge is slowly coming off. If you find yourself in this situation, locate a luthier (or stringed instrument specialist) and invest in getting your guitar fixed. If your guitar is particularly dirty, you may want to use a bit of soap. Grab your spray bottle with mild detergent in water. Then, moisten your dusting cloth. Do not spray the guitar directly, as the idea is to use as little water as possible. Use this moist cloth to wash off any dirt from your instrument.

Summary:
Inspect your bridge. Clean with detergent.