I have found that this site tends to be a decent guide on what you can expect for the test: http://www.tanos.co.uk/jlpt/jlpt4/grammar/GrammarList.N4.pdf Also, for grammar reference and practice, I recommend the "Nihongo Sou Matome" series. The explanations of the grammar are clear, however the exercises can be a little too easy, in my opinion. The "Kanzen Master" series is also really good. That will give many more useful exercises. Lastly, I would recommend renshuu.org, as their grammar dictionary provides awesome examples for every grammar point you will come across and it has really helped me understand it a lot better. I am currently between the N2 and N1 level and I still find it very useful. I hope this helps! Good luck in your studies!