Start with washed hair
Ask your boyfriend to wash his hair before you start cutting it. He should shampoo it properly and then leave the hair slightly wet.
Make three sections with a comb
Now you need to use the comb and divide his hair into three sections. Start by parting his hair to one side, separating the longer hair on the top from the shorter ones on the side. Then part his hair from the other side, creating three sections in total, one on the top and two on the sides.
Using your index and middle fingers you now need to pick a section of his hair from the top and raise it up straight to see the ends.
Hold the section taut and then clip the very end with the scissors so that a straight, level line is formed.
You must hold the scissors absolutely straight to get a clean uniformly leveled cut.
After clipping the edges off one section, pick an adjacent section and repeat the same steps. What you are doing basically is cutting his hair shorter and creating a uniform length.
You can ask him how short he wants you to cut, but remember, wet hair look longer but will shrink once they dry up, so don’t cut too close.
Now you need to move to the sides, which typically have shorter hair compared to the top. Here again you will need to set a baseline and then cut off the uneven edges to create a level.
However, you need to be more careful when snipping hair off the sides because there is less room for error here compared to the top, where you have longer hair to work with.
While the top section should be the same length all around, as you move down the back you need to start cutting closer.
An easier approach might be to start from the bottom baseline at the back, cutting it really short, and then moving up but reducing the length of your cuts.
If your boyfriend is willing you can use a hair clipper at the back, you can easily trim his hair using it. Just get the adjustable combs with the clipper and choose the longest one to stay on the safe side.
Finally, you can use a razor to clean up the base of his hair at the back, but make sure you do it very carefully and create a straight line.
Trim the sideburns
If your boyfriend has big sideburns, you might want to just trim them using the hair clipper. However, if he wants you to cut them short, start from the bottom and cut however much he wants using the scissors.
The correct way to do this is to place the scissor horizontally right above the edge of a sideburn and clipping it off.
That should complete the haircut. Good job!