I'm afraid there are no tricks but I'd suggest two things.
The long term approach: If you're committed to improve your writing skills, as ironic as it may sound, you should start to read as much as you can. In this way you will not only widen your vocabulary, but you'll start to recognise certain structures in the language that are vital, in this way you will end up learning grammar without even touching a grammar book.
The short term approach: For academic writing I'd recommend grabbing a list of conjunctions (they connect sentences). Pretty much you can get away with a limited vocabulary and a good understanding of how to connect two ideas on paper.
I hope this helps. I'm not a teacher, not even close.
Student or Learner