A legislator (a member of the legislature, a lawmaker) may introduce a proposed law for any reason or none. It may or may not be in response to a request by a member of the public. it may or may not follow a "process of reason" as to what is the best solution. It may be intended to be enacted, and the legislator may believe that it will be helpful to all, or it may be to make a political point, knowing that there is no chance of a bill passing.
The is no formal or standard process for the legislator to follow. Only once the bill is introduced is there a process, but the question says it is not about that process.
Some legislatures have a drafting service to assist in writing bills in proper legal language, so that they will have the desired effect if enacted. However, not all legislatures have such a service, and no lawmaker is required to use such a service.