Preparing For The Cut

Dry Haircutting
You must check the hair while it is dry to see how the client is currently wearing their hairstyle to identify any natural hair growth patterns and to feel the density and texture of the hair. Always carry out a porosity test on dry hair prior to the service.
Freehand and scissors over comb cutting techniques are best carried out on dry hair. Thinning scissors and clippers should only be used on dry hair.

Wet Haircutting
Always carry out an elasticity test on wet hair.

Once the hair has been shampooed and prepared for the service, check through the hair to identify the natural parting. On wet hair you will be able to see the hair type in its natural state, such as curly or straight, and recheck the movement of the hair.
The elasticity in the hair allows wet hair to be stretched up to 50% of its original length, and you must consider this when you are cutting the hair wet, as the dried result could be much shorter than you or your client anticipated. 

Guidelines
The guideline is the most important part of the haircut. If you are cutting and lose your guideline – STOP! The guideline determines the finished length of the cut and the overall shape and balance. Without a guideline you can not work methodically through the haircut or maintain accuracy. Even the most experienced stylists will follow a guideline.
Guidelines are the first cuts of the hairstyle. Your first cut in a baseline length; once the length has been agreed with your client, this becomes your guideline for the length of the haircut.
Once the baseline length has been agreed and cut, you are ready to begin the guideline for the internal layers of the hair. This internal guideline will help you achieve the shape of the style. Again, agree the desired length of the layers with your client and then cut in your internal guideline to suit the angle at which the hair will be cut.