The final step is to choose the most appropriate methods and reliable sources.
If you have to perform this kind of academic writing tasks, you should be ready to do it in the most convincing manner, give a proper description, aim, and key points, and also explain the accuracy of your chosen methods and sources.
We realize that it is not always possible and surely never easy.
Basically, writing a research proposal means preparing a work that would justify the topic you have chosen to study.
It is like a brief version of the actual thesis that presents the main points of the study.