The first step is surely to go for a nice haircut. This haircut is necessary because you need to achieve the look that you are going for. It will not be possible for you to trim your own hair with perfection that is required for a mohawk style. You should go for a side fade and a back side as well as an undercut if that is the style you are going for. Another option is to let the mohawk area of your hair grow out long enough to create a braided ponytail if that is the style you are opting for.
Finally what you need to do is use a good amount of hair product like hair wax for hair gel that can hold up your mohawk style. You need to use the hair product generously because you want your mohawk style to last all day long. Make sure you wash your hair every night to avoid causing any damage to your hairs by the chemical product.