Side Part & Hair Trimming

A: To be certain, you should discuss with the client specifically what he/she desires as the final result.
However, if the person tends to restyle her hair periodically in order to change her look, then you can shift to a center parting and do a uniform trimming of the perimeter. This will create a well-dispersed base length for the hair and prevent overly noticeable length discrepancies when the hair is styled in various ways.
The bottom line is simply this. As a hairdresser, our job is to give the client what they want for their hair. We advise them when they are lacking in perspective about what can reasonably be done with their hair. However, when all is said and done, we want the client to be happy. If we make sure to learn what the client wants, usually, the method of how to achieve that look is clear to us.
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See also:
Basic hair parting techniques
Why and how to trim hair
How often should I be trimming split-ends?