Prepare your moustache by using some warm water so that they got soft. Use a moustache comb to get them in shape so that you are able to trim them right. Having a haphazard moustache can lead to a haphazard trim.
Start from Edges
Start the trimming process from the outer parts of the moustache. Remember it is not a time to show your bravery and keeping your hand soft. Be artistic and have gentle strokes. Do not be impatient as you can cut more than you want or even flick off a side altogether.
Work Your Way Through
Slowly move around other areas of the moustache and get to the bottom and trim it carefully. You will have to make sure that you equally trim the bottom from both sides so that you have a good balance to your moustache.
The eventual fine tuning can be done with the help of a razor, especially from the top. Make sure that you have an even top as an out of shape top and sides look weird. You can also have a different styled moustache, such as one kept by Charlie Chaplin if you want to experiment.
Once again comb to see that the moustache is even after the trim. Closely examine after combing and correct anything that you seem to have underdone or over done. One again pay attention to this to make sure that you have some fine results.