Like a bridge connects two paths, simply in a guitar a bridge connects the strings from the body to the neck of the instrument. The bridge is one of the most essential parts of a guitar, as it is responsible for the tone, action and intonation. Bridges are of two kinds, one is known as the 'tremolo' which has an arm stretched below the string's anchor point. It looks like a lever which is used to manipulate the pitch of the instrument. The other type of bridge is 'non-tremolo', or more commonly known as the 'whammy bar'; this bridge comes without the lever and since it does not play a vital role in adjusting the pitch and is famously used for jazz music. Now that you know what is a bridge and its types, the next step is to learn how to adjust the guitar bridge.
The first step is to check the tuning of the instrument and the buzzing on the frets; check if the strings are breaking or the intonation maybe poor. The action must be checked, which is generally at the 12th fret. If it is high and therefore not buzzing properly, then you will have to have a look at the saddle. In case the string action is too high then the saddles must be lowered, as the strings will be over the fret board. If high string action is desired then the saddle has to be lowered. The saddles usually have two small screws which help in raising or lowering the saddle; it is advisable to use an Allen key for this action, avoiding the usage of your fingers. After completing this procedure, check the tuning of the guitar at the 12th fret again.
In case you have an acoustic guitar, then the bridge may be loose; usually due to heat, insufficient glue or a cracked bridge plate. In this case, you will have to completely remove the bridge from the instrument and then adjust the saddles. While adjusting the saddles, remember that turning the screws clockwise will raise the saddle and counter clockwise will lower it. Also always keep in mind that we are adjusting the saddles for up and down movement in the instrument; we can not adjust the back and forth movement.
If you want to avoid the tedious work of adjust or repairing, then ensure that you keep the saddle piece clean and check periodically for excessive wear or tear. Also avoid keeping the instrument in a hot environment, as it may lead to softening of the glue in the bridge, since it affects the location of the bridge on the body. If the strings at the saddle keep breaking more often, then the bridge certainly has some sharp edges.
Even though you have learnt the basic or amateur ways of adjusting, there might be instances when the guitar will be beyond your ability or understanding to repair or adjust. In such a scenario, immediately take your instrument to a professional who knows exactly how to adjust guitar bridge.