I am currently in the process of writing a manuscript on the Isotopy problem (Symplectic Geometry), but this was never my intention. It came about as I wrote another manuscript on the Oka Principle. I later recognized one problem would help solve, or lead others, in some fruitful way, to the solution of another.
In addition to extensive hours reading, investigating, and meditating; I have also communicated my ideas with a fellow professor at MIT; and thus far, the problems are still open, and my contribution could be beneficial to the field.
I suggest you look for open problems (if you're a mathematician), and give them a go, for the most part, I consider maths as an art. There just isn't a step-by-step guide on how to write a piece. It is built upon by many other pieces, One problem leads to another, and so forth