Christine Cheng (Lecturer in War Studies at King’s College London) has written a very useful blog post on how practitioners-turned-students, in particular, can learn to write academically by:
1. Building comprehension (read deeply and understand how the literature fits together)
2. Mimicing the academic form of your discipline (in terms of tone, style, presentation, use of language etc.)
3. Engaging with the literature and find your academic voice (critique existing literature and use it to build your own arguments)
4. Experimenting with new forms of expressing your ideas (optional)
The full article is here: The Art of Academic Writing (for Policy Makers & Everyone Else).