To begin creating a jutsu, you would need to have an idea of what you want to do and maybe take inspiration from another jutsu, like when Minato created the Rasengan, he was inspired by the Tailed Beast Ball. Also, to create a jutsu, you would need to figure out exactly how much chakra to use. You would need to decide what handseals are necessary to perform the jutsu properly and what nature of chakra you are going to use. To complete the jutsu you would need to keep trying it until it becomes perfect, and also make some different steps to make it easier to perform.