It is good practice to examine your violin each time you pick it up to play it. You want to look at its condition in general and a quick overall check goes a long way to stop expensive repairs in the future.
Firstly, examine the body of the violin for fine cracks, which can occur from sudden changes in temperature and humidity, being improperly handled or from the tension of the strings.
The Violin Bridge
The bridge should be in the right place and not leaving too far. Each time you tune the violin using the pegs, the top of the bridge moves a small amount towards the pegs. It is a small amount and usually not noticed. However, over time, this can cause the violin bridge to lean towards the fingerboard as the strings are tightened. The correct angle of the bridge can be determined by looking from the side of the bridge facing the tailpiece. It should be perpendicular to an imaginary straight line or tangent beginning at the point where the bridge rests on the curve of the violin. If the violin bridge leans too much off perpendicular, then the bridge may warp and possibly break. The correct position for the bridge is to align the feet of the bridge between the two small nicks on the inside of the two f-holes. To correct the violin bridge angle, you should lay the violin down on its back on a cloth or in its case. Rest your hands just above the widest part of the violin and grip the bridge between thumb and index finger or thumb and middle finger. There is a lot of pressure required to move the bridge. This must be done gradually without moving the placement of the feet.
Look at fine tuners should not be touching the wood of the instrument. You should look to make sure that there is a space between each tuner and the top of the instrument. Fine tuners have been known to have caused damage by digging into the wood in this manner.
Examine the pegs. They should move easily, but not slip too much. Either way, they may need attention. If a peg sticks too much, you can loosen it with commercial peg drops such as Hill Peg Compound. Be careful to do this one peg at a time. If you loosen too many strings at a time, you can also potentially damage the sound post because you are causing unequal pressure on the instrument. If you do not have peg drops, a small, dry scrap of soap can be used to rub a very small amount on the places where the peg passes through the peg box. Use sparingly! Conversely, if a peg is too loose, you can use blackboard chalk or pastels that artists use on the peg, as the chalk dust can help to hold the peg by causing friction. If the chalk does not seem to do the trick, this is a case where it would be advisable to take it to a luthier to refit the pegs.
Examine the violin strings on your instrument. Is there a build-up of rosin and dirt? Strings need to be changed periodically. As already discussed, the rosin is slightly acidic and so is the sweat and oils from your hands. This actually degrades the strings. An instrument that is played consistently will definitely need a new set of strings at least once every six months to a year.