Technique
With ingredients in a glass or tin (see safety technique), take muddler in hand and with force press down and apply a twisting motion. A proper muddled drink will have ingredients release all their essential oils, juices and flavors. When muddling fruit, one option is to add a few ice cubes (Ice can help break up the fruit and adds a little water to your cocktail).
Muddling too much or too little? Not enough will leave you with a drink that was a waste of time and too much muddling may release bitterness found in some fruit peels and herbs. A good rule of thumb is 8-13 pressurized passes with the Mr. Mojito muddler that will leave you with a delicious cocktail.
Safety
When you are muddling at home always use a tin. Professional bartenders use a special heat tempered glass that is more durable than glassware found in the home. When muddling in a glass always take great care.
Seek out mixing glasses that are heat tempered and have a "T" on the bottom of the glass.
Never muddle in any other glass. Use at your own risk. For fail safe muddling the use of a metal mixing tin is recommended.