After you conclude your initial literature review, monitor new literature as you continue to research and write about your topic.
Bibliographic databases
For this purpose, see the documentation for bibliographic databases or journals to see if they enable alerts of
Preprint alerts
Also, if you want to monitor preprints, see if preprint server(s) in your subject enable alerts. Example.
If a preprint server does not have an email alert for new content, consider setting up Google Scholar alerts.
Browzine
Social media
For an analysis of social media as a vehicle for learning about new scientific discoveries, see The Science People See on Social Media (Pew Research Center, 2018)