In writing, we use the acronym of SLAMS. I know there are different ones out there (RACE, etc). I find this one to be the most helpful.
Each letter in SLAMS stands for something important that can be applied to either an extended response or a constructed response on any type of open ended question. I teach the kids to say "A good answer SLAMS the question". We use this starting in January to help make sure our answers are the best they can be. You can download this free poster by clicking on the picture.
We also do some test prep activities twice a week. Just enough to where we are practicing but not overwhelmingly so! I incorporate 'cold read' passages every week as well so I can focus on their independent comprehension. These are SO important. We so often 'prep' our students on their weekly comprehension stories - even by just reading it to them. We need to see what they can do on their own.
The other piece that's critical that I do is teach my students important 'testing' vocabulary. We do a program all year long called "Vocabulary Voyage". It teaches the students a variety of words they might see on a standardized test. We learn 5 words every two weeks. The first week we learn the definitions of those 5 words. The 2nd week we learn how to answer questions with those words in them. I have found that a lot of time when students are presented with the 'test' they have the knowledge but the questions are worded in a way that they just don't understand. This program is designed to help them with that! They also learn how to sight read the words as well. The words hang outside the door and we say the word of the day as we enter the classroom each time.
Other than those components, I really don't 'prep' them that much. I try throughout the year to use best practices that will give them as much firepower for the test as I can. We can then only hope for the best. I wish you all the best of luck with your upcoming testing. :) Let me know if you have any questions!