Instruments are tuned using the tuning pegs and the fine tuners.
Because the tuning pegs are used for gross adjustments, the fine tuners are very helpful in making small tuning adjustments. The fine tuners generally should be kept in the middle range position, not too far in or out.
When a fine tuner is most of the way in or out, reset it to the middle-range position and use the tuning peg to tune the string. Then, use the fine tuner to make the final adjustments.
Again, when tuning your instrument, do not go above the correct pitch of the string. If a string is not in tune, turn the peg down, then slowly up. Repeat this until the string is properly tuned. Check once a week to make sure your bridge is standing up straight.
Tilted bridges can become warped or fall over and damage the instrument. Ask your teacher or a violin maker to help you straighten it.
For more guides on string instrument care, venture here.