First of all, you need to comb your moustache downwards which will keep all hair of your moustache a similar direction and will make it easy to trim in a desired manner.
Now take a trimmer and start trimming your moustache from the edges of your moustache. Make sure you follow the line or edge of upper lip which will help you in trimming your moustache in a balanced manner.
You should lift the hair of your moustache and comb it gently which will help you to identify the longer hair that should be cut. After trimming your moustache from downwards or from the edges of the hair, you should check the balance whether the hair are straight or are balanced or not.
Make sure you use the trimmer in a careful way in order to avoid cutting hair in an imbalance or unwanted way. Sometimes people fail to handle the trimmer in an appropriate manner while trimming their moustache and end up in cutting the hair in a rough way.
After completing a round of trimmer, comb your hair downwards in order to check whether they are in straight and balanced shape or not.
Use a hair removing machine to remove the unwanted small hairs besides the moustache that are disturbing a clean look to your moustache.
In the end, you should remove the hairs from the outer edges of your nostrils in order to give a clean and perfect touch of your moustache from all sides.
Always try to trim your moustache with a good quality trimmer that does not pull hair from their roots which will make it easy for you to trim your moustache at home.